drm/amd/display: Increase HDMI AV mute wait from 2 to 3 frames

drm/amd/display: Increase HDMI AV mute wait from 2 to 3 frames

Some HDMI sinks need additional GCP packets to properly process the
mute state before the timing generator is disabled, especially after
link re-establishment with HDMI 2.0 scrambling enabled. Waiting for
only 2 frames is insufficient for certain monitor firmware, resulting
in garbled display output on resume from suspend.

Increase the AV mute wait in dcn30_set_avmute() from 2 to 3 frames
to ensure the sink receives enough GCP packets.

Closes: https://gitlab.freedesktop.org/drm/amd/-/work_items/5167
Assisted-by: Cursor:Claude-Opus-4.6
Reviewed-by: Wayne Lin <wayne.lin@amd.com>
Signed-off-by: Ray Wu <ray.wu@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 0c0d5174b09640d8b560764aa5a177630e076e93)
Cc: stable@vger.kernel.org