drm/amd/display: Remove incorrect checking in dmub aux handler

drm/amd/display: Remove incorrect checking in dmub aux handler

[Why & How]
"Request length != reply length" is expected behavior defined in spec.
It's not an invalid reply. Besides, replied data handling logic is not
designed to be written in amdgpu_dm_process_dmub_aux_transfer_sync().
Remove the incorrectly handling section.

Fixes: ead08b95fa50 ("drm/amd/display: Fix race condition in DPIA AUX transfer")
Cc: Mario Limonciello <mario.limonciello@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Ray Wu <ray.wu@amd.com>
Signed-off-by: Wayne Lin <Wayne.Lin@amd.com>
Signed-off-by: Ray Wu <ray.wu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>