ubi: merge changes from msm-3.18 kernel to msm-4.14 kernel

This commit has the following commits:

'commit e81a5c26e7b5 ("ubi: Add scrub_all support to UBI")'
'commit a9e78113fe84 ("ubi: Fix ubi_io_write_vid_hdr so it
can be used before wl init")'
'commit e2b9f56d5ace ("UBI: Do not re-erase the PEB before
writing the VID header")'
'commit d538879e7328 ("UBI: Re-erase the PEB before writing
the VID header")'

Also fixed few static analysis and checkpatch errors.

Change-Id: Ifafb82fe4ddb7120277dcfbbff79b3e087ca344d
Signed-off-by: Nikhilesh Reddy <reddyn@codeaurora.org>
Signed-off-by: Anjana <ahari@codeaurora.org>