the mount command used to have the syntax 'mount <dev> <type> <mountpoint>'.
This was changed to the more Linux like behaviour which specifies the
type with the -t <type> option. If a newer barebox is run on a device
with an older environment the mount command no longer works. This patch
adds compatibility to the old behaviour.
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>