drm/amdgu: remove unused code

The same code is executed when the condition err is true or false,
because the code in the if-then branch and after the if statement is identical

Signed-off-by: Jesse Zhang <Jesse.Zhang@amd.com>
Reviewed-by: Tim Huang <Tim.Huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>