drm/i915/dp: Make has_gamut_metadata_dip() non static

drm/i915/dp: Make has_gamut_metadata_dip() non static

Make has_gamut_metadata_dip() non static so it can also be used to
at other places eg in intel_dp_aux_backlight. So that we can check
if HW is capable of sending SDP which helps us decide if we use
AUX based HDR control or via SDP.

--v2
-State reason the function is needed [Arun]

Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Arun R Murthy <arun.r.murthy@intel.com>
Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240507040407.1056061-2-suraj.kandpal@intel.com