drm/i915/dsi: let HW maintain the HS-TRAIL timing

drm/i915/dsi: let HW maintain the HS-TRAIL timing

This change is to avoid over-specification of the TEOT timing
parameter, which is derived from software in current design.

Supposed that THS-TRAIL and THS-EXIT have the minimum values,
i.e., 60 and 100 in ns. If SW is overriding the HW default,
the TEOT value becomes 150 ns, approximately calculated by
the following formula.

  DIV_ROUND_UP(60/50)*50 + DIV_ROUND_UP(100/50))*50/2, where 50
  is LP Escape Clock time in ns.

The TEOT value 150 ns is larger than the maximum value,
around 136 ns if UI is 1.8ns, (105 ns + 12*UI, defined by MIPI
DPHY specification).

However, the TEOT value will meet the specification if THS-TRAIL
is set to the HW default, instead of software overriding.

The timing change is made for both data lane and clock lane.

v1: initial version.
v2: change clock lane dphy timings.
v3: remove calculation of trail cnt.
v4: rebase.

Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/13891
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Vandita Kulkarni <vandita.kulkarni@intel.com>
Cc: Lee Shawn C <shawn.c.lee@intel.com>
Cc: Cooper Chiou <cooper.chiou@intel.com>
Signed-off-by: William Tseng <william.tseng@intel.com>
Acked-by: Vandita Kulkarni <vandita.kulkarni@intel.com>
Link: https://lore.kernel.org/r/20250311100626.533888-1-william.tseng@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>