[media] dvb-frontends: get rid of some "always false" warnings

On gcc, enums are generally unsigned, except if a negative value
is declared. Due to that, warnings may happen there:
drivers/media/dvb-frontends/cx22700.c:142:2: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits]
drivers/media/dvb-frontends/cx22700.c:155:2: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits]
drivers/media/dvb-frontends/cx24123.c:341:2: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits]
drivers/media/dvb-frontends/l64781.c:183:2: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits]
drivers/media/dvb-frontends/l64781.c:187:2: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits]
drivers/media/dvb-frontends/mt312.c:552:2: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits]
drivers/media/dvb-frontends/mt312.c:560:2: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits]
As other compilers might be using signed values, the better is to
keep the checks there, casting the value to avoid the warning.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/dvb-frontends/cx22700.c

@@ -139,7 +139,7 @@ static int cx22700_set_tps(struct cx22700_state *state,
 	if (p->code_rate_HP == FEC_4_5 || p->code_rate_LP == FEC_4_5)
 		return -EINVAL;
 
-	if (p->guard_interval < GUARD_INTERVAL_1_32 ||
+	if ((int)p->guard_interval < GUARD_INTERVAL_1_32 ||
 	    p->guard_interval > GUARD_INTERVAL_1_4)
 		return -EINVAL;
 
@@ -152,7 +152,7 @@ static int cx22700_set_tps(struct cx22700_state *state,
 	    p->modulation != QAM_64)
 		return -EINVAL;
 
-	if (p->hierarchy < HIERARCHY_NONE ||
+	if ((int)p->hierarchy < HIERARCHY_NONE ||
 	    p->hierarchy > HIERARCHY_4)
 		return -EINVAL;
 

drivers/media/dvb-frontends/cx24123.c

@@ -338,7 +338,7 @@ static int cx24123_set_fec(struct cx24123_state *state, fe_code_rate_t fec)
 {
 	u8 nom_reg = cx24123_readreg(state, 0x0e) & ~0x07;
 
-	if ((fec < FEC_NONE) || (fec > FEC_AUTO))
+	if (((int)fec < FEC_NONE) || (fec > FEC_AUTO))
 		fec = FEC_AUTO;
 
 	/* Set the soft decision threshold */

drivers/media/dvb-frontends/l64781.c

@@ -180,11 +180,11 @@ static int apply_frontend_param(struct dvb_frontend *fe)
 	    p->transmission_mode != TRANSMISSION_MODE_8K)
 		return -EINVAL;
 
-	if (p->guard_interval < GUARD_INTERVAL_1_32 ||
+	if ((int)p->guard_interval < GUARD_INTERVAL_1_32 ||
 	    p->guard_interval > GUARD_INTERVAL_1_4)
 		return -EINVAL;
 
-	if (p->hierarchy < HIERARCHY_NONE ||
+	if ((int)p->hierarchy < HIERARCHY_NONE ||
 	    p->hierarchy > HIERARCHY_4)
 		return -EINVAL;
 

drivers/media/dvb-frontends/mt312.c

@@ -549,15 +549,15 @@ static int mt312_set_frontend(struct dvb_frontend *fe)
 	    || (p->frequency > fe->ops.info.frequency_max))
 		return -EINVAL;
 
-	if ((p->inversion < INVERSION_OFF)
+	if (((int)p->inversion < INVERSION_OFF)
 	    || (p->inversion > INVERSION_ON))
 		return -EINVAL;
 
 	if ((p->symbol_rate < fe->ops.info.symbol_rate_min)
 	    || (p->symbol_rate > fe->ops.info.symbol_rate_max))
 		return -EINVAL;
 
-	if ((p->fec_inner < FEC_NONE)
+	if (((int)p->fec_inner < FEC_NONE)
 	    || (p->fec_inner > FEC_AUTO))
 		return -EINVAL;