drm/amdgpu: Update PSP TA unload function

Update PSP TA unload function to use PSP TA context as input argument.

Signed-off-by: Candice Li <candice.li@amd.com>
Reviewed-by: John Clements <john.clements@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>