drm/amdgpu: Create common PSP TA load function

Creat common PSP TA load function and update PSP ta_mem_context
with size information.

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>