ANDROID: mm: shmem: Use memfd-ashmem-shim ioctl handler

Allow the memfd-ashmem-shim ioctl handler to run for any shmem file,
so that memfds can handle ashmem ioctl commands.

While this allows ashmem ioctl commands to be invoked on more than just
memfds, this should be fine, since the ioctl commands don't expose any
additional functionality than what is already achievable via other
system calls.

Bug: 111903542
Change-Id: I0bf57ac5a90dba66e5c2c32beff70bcf9d26db6b
Signed-off-by: Isaac J. Manjarres <isaacmanjarres@google.com>