Revert "drm/i915/dp: Reject HBR3 when sink doesn't support TPS4"

This reverts commit 584cf613.
Commit 584cf613 ("drm/i915/dp: Reject HBR3 when sink doesn't support
TPS4") introduced a blanket rejection of HBR3 link rate when the sink does
not support TPS4.

While this was intended to address instability observed on certain eDP
panels [1], there seem to be edp panels that do not follow the
specification. These eDP panels do not advertise TPS4 support, but require
HBR3 to operate at their fixed native resolution [2].

As a result, the change causes blank screens on such panels. Apparently,
Windows driver does not enforce this restriction, and the issue is not seen
there.

Therefore, revert the commit to restore functionality for such panels,
and align behaviour with Windows driver.

[1] https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/5969
[2] https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/14517

v2: Update the commit message with better justification. (Ville)

Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/14517


Acked-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Link: https://lore.kernel.org/r/20250710052041.1238567-2-ankit.k.nautiyal@intel.com