drm/i915: Use _MMIO_PIPE3() for ilk+ WM0_PIPE registers

Remove the hand rolled array of WM0_PIPE register offsets
and use the standard _MMIO_PIPE3() instead.

v2: Take care of gvt too

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181212211738.27770-1-ville.syrjala@linux.intel.com


Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>