Commit 4f2a572e ("drm/i915/userptr: Never allow userptr into the
mappable GGTT") made I915_GEM_MMAP_GTT IOCTLs to fail when attempted
on a userptr object in order to protect from a lockdep splat.  Later
on, new mapping types were introduced by commit cc662126
("drm/i915: Introduce DRM_I915_GEM_MMAP_OFFSET").  Those new mapping
types suffer from the same lockdep splat issue but they now succeed
when tried on top of a userptr object.  Fix it.

v2: Don't play with the -ENODEV driver response (Chris)
Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
Cc: Abdiel Janulgue <abdiel.janulgue@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20200204162302.1299516-1-chris@chris-wilson.co.uk