Similar to mount(8) the barebox command mount now supports passing a string
to the file system driver via -o.
This is used in the next commit to let the user specify port numbers for
nfs mounts.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>