Staging: vme: silence a Sparse warning

Sparse complains that "arg" is not a __user pointer.  The "argp" and
"arg" variables are equivalent but argp is declared as a __user pointer.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-By: Martyn Welch <martyn.welch@ge.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>