UIO: allow binding uio_pdrv_genirq.c to devices using command line option

This adds ability to bind uio driver to given open firmware device
using command line option. Thus, userspace driver can be developed and
used without modifying the kernel.

Signed-off-by: Pavel Machek <pavel@denx.de>
Tested-by: Detlev Zundel <dzu@denx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>