drm/amdgpu: just disallow reading untouched registers

Not sure what the original intention was here, but returning a random piece of
kernel memory to userspace because we didn't set the value at all is clearly
not a good idea.

This patch disallows reading the register and returns
a proper error code instead.

Signed-off-by: Christian König <christian.koenig@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Tom St Denis <tom.stdenis@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/vi.c

@@ -464,15 +464,9 @@ static void vi_detect_hw_virtualization(struct amdgpu_device *adev)
 }
 
 static const struct amdgpu_allowed_register_entry tonga_allowed_read_registers[] = {
-	{mmGB_MACROTILE_MODE7, true},
 };
 
 static const struct amdgpu_allowed_register_entry cz_allowed_read_registers[] = {
-	{mmGB_TILE_MODE7, true},
-	{mmGB_TILE_MODE12, true},
-	{mmGB_TILE_MODE17, true},
-	{mmGB_TILE_MODE23, true},
-	{mmGB_MACROTILE_MODE7, true},
 };
 
 static const struct amdgpu_allowed_register_entry vi_allowed_read_registers[] = {