drm/i915: s/glk_read_lut_10/bdw_read_lut_10/

glk_read_lut_10() works just fine for all bdw+ platforms, so
rename it.

Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200925131656.10022-5-ville.syrjala@linux.intel.com