drm/i915: remove excess line continuation backslashes

While removing .palette_offsets, I removed the commas after
.trans_offsets in the macros, but failed to remove the line continuation
backslashes.

While at it, also remove another extra comma to be in line with the
other related macros.

Fixes: 74c1e826

 ("drm/i915: remove palette_offsets from device info in favor of _PICK()")
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181114112130.22264-1-jani.nikula@intel.com