busybox/mdev-mount.sh: Fix partition detect and cleanup mountpoint on fail
This fixes issues mainly seen when mounting eMMC devices:
The wildcard /sys/block/${DEVBASE}/${DEVBASE}*1 matches both "mmcblk0p1"
and "mmcblk0boot1" for example, and this results in syntax errors. Fix this
by searching for a "partition" file instead, which only exists for real
partitions and not 'fakes' like the eMMC extra's.
When mount fails, the mountpoint file is left behind, causing later attempts
at auto-mounting it to fail. If mount fails, remove the mountpoint, leaving
the system in the state as it was before the mount attempt.
Signed-off-by: Mike Looijmans <mike.looijmans@topic.nl> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
