drm/amdgpu: cache psp runtime boot_cfg_bitmask in sw_int

PSP runtime boot_cfg_bitmask carries various psp bl
feature bit mask that can be used by driver. Cache
it in sw_init for further usage.

Signed-off-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: John Clements <john.clements@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>