call arguments.  Hence, init's
  execve ("/bin/sh", ...)
failed with error code EFAULT.

There's room for improvement here: in case people want to have filesystems
on flash rather than in main memory, _access_ok should be modified to
allow this.

This bug fix is also dedicated to Michael Hennerich.

Signed-off-by: Bernd Schmidt <bernds_cb1@t-online.de>
Signed-off-by: Bryan Wu <cooloney@kernel.org>