drm/i915: Combine .compute_{pipe,intermediate}_wm() into one

drm/i915: Combine .compute_{pipe,intermediate}_wm() into one

We always call .compute_pipe_wm() and .compute_intermediate_wm()
back to back. Just combine them to a single hook for simplicity.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240916162413.8555-3-ville.syrjala@linux.intel.com
Reviewed-by: Vinod Govindapillai <vinod.govindapillai@intel.com>