drm/i915: Don't register the CRT connector when it's fused off on LPT-H

LPT-H has a strap bit for fused off CRT block. Check it to see if
we should register the CRT connector or not. Supposedly this also
forces the ADAP enable bit to 0, so the detection we added in
commit 6c03a6b ("drm/i915: Don't register CRT connector when it's fused off")
should already catch it, but checking the fuse bit should at least
do no harm.

v2: Use HAS_PCH_LPT_H() (Paulo)

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1449005335-15192-1-git-send-email-ville.syrjala@linux.intel.com

drivers/gpu/drm/i915/i915_reg.h

@@ -7556,6 +7556,7 @@ enum skl_disp_power_wells {
 #define SFUSE_STRAP			_MMIO(0xc2014)
 #define  SFUSE_STRAP_FUSE_LOCK		(1<<13)
 #define  SFUSE_STRAP_DISPLAY_DISABLED	(1<<7)
+#define  SFUSE_STRAP_CRT_DISABLED	(1<<6)
 #define  SFUSE_STRAP_DDIB_DETECTED	(1<<2)
 #define  SFUSE_STRAP_DDIC_DETECTED	(1<<1)
 #define  SFUSE_STRAP_DDID_DETECTED	(1<<0)

drivers/gpu/drm/i915/intel_display.c

@@ -14257,6 +14257,9 @@ static bool intel_crt_present(struct drm_device *dev)
 	if (IS_CHERRYVIEW(dev))
 		return false;
 
+	if (HAS_PCH_LPT_H(dev) && I915_READ(SFUSE_STRAP) & SFUSE_STRAP_CRT_DISABLED)
+		return false;
+
 	if (IS_VALLEYVIEW(dev) && !dev_priv->vbt.int_crt_support)
 		return false;