drm/i915: Precompute can_sagv for each wm level

drm/i915: Precompute can_sagv for each wm level

In order to remove intel_atomic_crtc_state_for_each_plane_state()
from skl_crtc_can_enable_sagv() we can simply precompute whether
each wm level can tolerate the SAGV block time latency or not.

This has the nice side benefit that we remove the duplicated
wm level latency calculation. In fact the copy of that code
we had in skl_crtc_can_enable_sagv() didn't even handle
WaIncreaseLatencyIPCEnabled/Display WA #1141 whereas the copy
in skl_compute_plane_wm() did. So now we just have the one
copy which handles all the w/as.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201106173042.7534-5-ville.syrjala@linux.intel.com
Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>