busybox-mdev: avoid unmounting/mounting /dev/pts when redundant
busybox-mdev: avoid unmounting/mounting /dev/pts when redundant

Certain combinations of kernel config and /etc/fstab might mean that
/dev/pts and/or /dev/shm are already mounted. When we're not mounting
our own filesystem on top of /dev, there's no reason to unmount them
and remount them afterwards.

oe-lite/base,oe-lite/base,oe-lite/base,oe-lite/base,oe-lite/base,oe-lite/base