anv: fix unwind of vkCreateDevice fail

We're skipping the context destruction in some cases which is the
grand scheme of thing is not that important because closing device->fd
will destroy the associated context as well.

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reported-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Cc: <mesa-stable@lists.freedesktop.org>
Fixes: b30e01ae ("anv: fix memory leak on device destroy")
(cherry picked from commit 0dfa643f)