drm/i915/dp: Pass only the required i915 to intel_dp_source_dsc_version_minor()

intel_dp_source_dsc_version_minor() only requires the i915 pointer, so pass
only this to the function.

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231006133727.1822579-12-imre.deak@intel.com