drm/i915: Rename HAS_GMCH

First of all GMCH can be considered a feature by itself
since it is a chip present in some platforms that connects
the IA processor to memory and other components in PC.

Also with the introduction of display block at device info,
we got a redundant definition:

.display.has_gmch_display = 1,

So, let's clean up things a bit and use the standardized
way of has_feature on displays side.

No functional change and no manual interaction to generate
this patch.

It is only:

sed -si -e 's/has_gmch_display/has_gmch/g' \
    	-e 's/HAS_GMCH_DISPLAY/HAS_GMCH/g' drivers/gpu/drm/i915/*{c,h}

Cc: José Roberto de Souza <jose.souza@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190204222538.15842-1-rodrigo.vivi@intel.com