vme: Update documentation to match api

The vme_register_driver() api changed in commit 5d6abf37 ("staging:
vme: make match() driver specific to improve non-VME64x support") but the
documentation wasn't updated. Update the documentation to match the API.

Signed-off-by: Martyn Welch <martyn@welchs.me.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>