drm/amd/display: Add additional checks for PSP footer size

drm/amd/display: Add additional checks for PSP footer size

[WHY & HOW]
Newer ASICs have different PSP footer sizes which lead to driver
failing to locate the DMCUB FW meta info, which in turn causes
improper DMCUB FW loading and causes DMCUB to crash.

Add support for custom PSP footer sizes and check 512B by default
as well.

Reviewed-by: Charlene Liu <charlene.liu@amd.com>
Signed-off-by: Ovidiu Bunea <ovidiu.bunea@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>