net: gianfar_ptp: Rename FS bit to FIPERST

FS is a global symbol used by the x86 32-bit architecture, fixes builds
re-definitions:

>> drivers/net/ethernet/freescale/gianfar_ptp.c:75:0: warning: "FS"
>> redefined
    #define FS                    (1<<28) /* FIPER start indication */

   In file included from arch/x86/include/uapi/asm/ptrace.h:5:0,
                    from arch/x86/include/asm/ptrace.h:6,
                    from arch/x86/include/asm/math_emu.h:4,
                    from arch/x86/include/asm/processor.h:11,
                    from include/linux/mutex.h:19,
                    from include/linux/kernfs.h:13,
                    from include/linux/sysfs.h:15,
                    from include/linux/kobject.h:21,
                    from include/linux/device.h:17,
                    from
drivers/net/ethernet/freescale/gianfar_ptp.c:23:
   arch/x86/include/uapi/asm/ptrace-abi.h:15:0: note: this is the
location of the previous definition
    #define FS 9

Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/freescale/gianfar_ptp.c

@@ -72,7 +72,7 @@ struct gianfar_ptp_registers {
 /* Bit definitions for the TMR_CTRL register */
 #define ALM1P                 (1<<31) /* Alarm1 output polarity */
 #define ALM2P                 (1<<30) /* Alarm2 output polarity */
-#define FS                    (1<<28) /* FIPER start indication */
+#define FIPERST               (1<<28) /* FIPER start indication */
 #define PP1L                  (1<<27) /* Fiper1 pulse loopback mode enabled. */
 #define PP2L                  (1<<26) /* Fiper2 pulse loopback mode enabled. */
 #define TCLK_PERIOD_SHIFT     (16) /* 1588 timer reference clock period. */
@@ -502,7 +502,7 @@ static int gianfar_ptp_probe(struct platform_device *dev)
 	gfar_write(&etsects->regs->tmr_fiper1, etsects->tmr_fiper1);
 	gfar_write(&etsects->regs->tmr_fiper2, etsects->tmr_fiper2);
 	set_alarm(etsects);
-	gfar_write(&etsects->regs->tmr_ctrl,   tmr_ctrl|FS|RTPE|TE|FRD);
+	gfar_write(&etsects->regs->tmr_ctrl,   tmr_ctrl|FIPERST|RTPE|TE|FRD);
 
 	spin_unlock_irqrestore(&etsects->lock, flags);