drm/amd/display: Fix PSR-SU not support but still call the amdgpu_dm_psr_enable

[Why]
The enum DC_PSR_VERSION_SU_1 of psr_version is 1 and
DC_PSR_VERSION_UNSUPPORTED is 0xFFFFFFFF.

The original code may has chance trigger the amdgpu_dm_psr_enable()
while psr version is set to DC_PSR_VERSION_UNSUPPORTED.

[How]
Modify the condition to psr->psr_version == DC_PSR_VERSION_SU_1

Reviewed-by: Sun peng Li <sunpeng.li@amd.com>
Signed-off-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Roman Li <roman.li@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>