seccomp: Fix ioctl number for SECCOMP_IOCTL_NOTIF_ID_VALID

When SECCOMP_IOCTL_NOTIF_ID_VALID was first introduced it had the wrong
direction flag set. While this isn't a big deal as nothing currently
enforces these bits in the kernel, it should be defined correctly. Fix
the define and provide support for the old command until it is no longer
needed for backward compatibility.

Fixes: 6a21cc50 ("seccomp: add a return code to trap to userspace")
Signed-off-by: Kees Cook <keescook@chromium.org>