drm/i915/dp: Remove HAS_DSC macro for intel_dp_dsc_max_src_input_bpc

DSC support is already checked before the helper
intel_dp_dsc_max_src_input_bpc is called.
Remove the check from the helper.

v2: Drop the argument struct drm_i915_private *i915. (Suraj)

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241217093244.3938132-6-ankit.k.nautiyal@intel.com