drm/i915/vdsc: Add func to get no. of vdsc instances per pipe

We have a function that gets us the total of the vdsc engines being
used but not the no. of vdsc instances being used by each pipe.

--v6
-Change function to static

--v7
-Shorten name to intel_dsc_get_vdsc_per_pipe
Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Signed-off-by: Animesh Manna <animesh.manna@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230828054300.560559-4-suraj.kandpal@intel.com