drm/amd/display: Use HW lock mgr for PSR1 when only one eDP

[WHY]
DMUB locking is important to make sure that registers aren't accessed
while in PSR.  Previously it was enabled but caused a deadlock in
situations with multiple eDP panels.

[HOW]
Detect if multiple eDP panels are in use to decide whether to use
lock. Refactor the function so that the first check is for PSR-SU
and then replay is in use to prevent having to look up number
of eDP panels for those configurations.

Fixes: f245b400 ("Revert "drm/amd/display: Use HW lock mgr for PSR1"")
Closes: drm/amd#3965


Reviewed-by: ChiaHsuan Chung <chiahsuan.chung@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit ed569e12)
Cc: stable@vger.kernel.org