drm/amd/display: Prevent PSR from being enabled if initialization fails

[Why]
PSR_SET command is sent to the microcontroller in order to initialize
parameters needed for PSR feature, such as telling the microcontroller
which pipe is driving the PSR supported panel. When this command is
skipped or fails, the microcontroller may program the wrong thing if
driver tries to enable PSR.

[How]
If PSR_SET fails, do not set psr_enable flag to indicate the feature is
not yet initialized.

Signed-off-by: Anthony Koo <Anthony.Koo@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>