drm/i915: Start passing latency as parameter

We need to start passing memory latency as a
parameter when calculating plane wm levels,
as latency can get changed in different
circumstances(for example with or without SAGV).
So we need to be more flexible on that matter.

v2: Changed latency type from u32 to unsigned int(Ville Syrjälä)

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200409154730.18568-2-stanislav.lisovskiy@intel.com