drm/i915/dp: Compute as_sdp.vtotal based on vrr timings

Compute as_sdp.vtotal based on minimum vtotal calculated
during vrr computation.

--v2:
 - make a separate patch and update to vmin only [Ankit].

--v3:
 - Update vtotal to vmin for cmrr case as well [Ankit].

--v4:
 - update vtotal with wrapper function of vmin [Ville]

Signed-off-by: Mitul Golani <mitulkumar.ajitkumar.golani@intel.com>
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250130051609.1796524-5-mitulkumar.ajitkumar.golani@intel.com