Backport UBI patches from 4.5 rc3

UBIFS over UBI is the default filesystem used in QCOM chipsets
that use NAND storage.

Recently a number of stability and performance fixes were
added to the kernel that address issues ranging from data loss,
memory leaks and bootup issues. Some debug logs were also improved.
There were also some fixes to the fastboot code

Backport and bring in all the changes to ensure stability and
better performance for the NAND based devices.

* The patches included are :
  mtd: ubi: wl: avoid erasing a PEB which is empty
  mtd: ubi: don't leak e if schedule_erase() fails
  mtd: ubi: fixup error correction in do_sync_erase()
  UBI: fix use of "VID" vs. "EC" in header self-check
  UBI: fix return error code
  UBI: Remove in vain semicolon
  UBI: Fastmap: Fix PEB array type
  ubi: fastmap: Implement produce_free_peb()
  UBI: drop null test before destroy functions
  UBI: Fix debug message
  UBI: Fix typo in comment
  UBI: Fastmap: Simplify expression
  UBI: Update comments to reflect UBI_METAONLY flag
  UBI: return ENOSPC if no enough space available
  UBI: Validate data_size
  ubifs: Use XATTR_*_PREFIX_LEN
  UBIFS: add a comment in key.h for unused parameter
  ubifs: Remove unused security xattr handler
  ubifs: introduce UBIFS_ATIME_SUPPORT to ubifs
  ubifs: make ubifs_[get|set]xattr atomic
  UBIFS: Delete unnecessary checks before the function call "iput"
  UBIFS: Fix possible memory leak in ubifs_readdir()
  fs/ubifs: remove unnecessary new_valid_dev check
  UBIFS: print verbose message when rescanning a corrupted node
  UBIFS: call dbg_is_power_cut() instead of reading c->dbg->pc_happened
  UBIFS: fix a typo in comment of ubifs_budget_req
  UBIFS: use kmemdup rather than duplicating its implementation
  UBIFS: Kill unneeded locking in ubifs_init_security

CRs-Fixed: 978252
Change-Id: Iebdd96cc6c95fd1b0fc19228ca00bd63c5b06119
Signed-off-by: Nikhilesh Reddy <reddyn@codeaurora.org>