drm/amdgpu: Save VCN shared memory with init reset

VCN shared memory is in framebuffer and there are some flags initialized
during sw_init. Ideally, such programming should be during hw_init.

Make sure the flags are saved during reset on initialization since that
reset will affect frame buffer region. For clarity, separate it out to
another function.

Fixes: 1e4acf4d ("drm/amdgpu: Add reset on init handler for XGMI")
Signed-off-by: Lijo Lazar <lijo.lazar@amd.com>
Reported-by: Hao Zhou <hao.zhou@amd.com>
Reviewed-by: Leo Liu <leo.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>