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 <[e-mail]>
Acked-by: Alex Deucher <[e-mail]>
Acked-by: Tom St Denis <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

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

···
 }
 
 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[] = {