Out of the entire GART/VM subsystem, the hw designers changed
the location of 3 regs.

v2: airlied: add parameter for userspace to work from.
Signed-off-by: NAlex Deucher <alexdeucher@gmail.com>
Signed-off-by: NJerome Glisse <jglisse@redhat.com>
Cc: stable@kernel.org
Signed-off-by: NDave Airlie <airlied@redhat.com>