Clean up /dev mounting and use devtmpfs.
Note that config DEVTMPFS_MOUNT says ...
"This option does not affect initramfs based booting, here
the devtmpfs filesystem always needs to be mounted manually
after the roots is mounted."

Signed-off-by: David Greaves <david.greaves@jollamobile.com>
Merge pull request #7 from lbt/hybris-10.1

Clean up /dev mounting and use devtmpfs.