ioctl_userfaultfd.2: Corrections for returned .ioctls members

ioctl_userfaultfd.2: Corrections for returned .ioctls members

Support for the `UFFDIO_WRITEPROTECT` operation is not indicated in the
`ioctls` member of `struct uffdio_api`.  It is indicated in the `ioctls`
member of `struct uffdio_register` along with indications of support for
the `UFFDIO_COPY`, `UFFDIO_WAKE` and `UFFDIO_ZEROPAGE` operations (and
also the `UFFDIO_CONTINUE` operation supported since Linux 5.13 but
that is not documented by this man page yet.)

Fixes: f559fa36a678 ("ioctl_userfaultfd.2: Add write-protect mode docs")
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Acked-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>