drm/amdgpu: disallow direct upload save restore list from gfx driver

Direct uploading save/restore list via mmio register writes breaks the security
policy. Instead, the driver should pass s&r list to psp.

For all the ASICs that use rlc v2_1 headers, the driver actually upload s&r list
twice, in non-psp ucode front door loading phase and gfx pg initialization phase.
The latter is not allowed.

VG12 is the only exception where the driver still keeps legacy approach for S&R
list uploading. In theory, this can be elimnated if we have valid srcntl ucode
for VG12.

Signed-off-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: Candice Li <Candice.Li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>