nand_partitions: Implement hack to swap /system and /userdata

This hack will swap the /system and /userdata partition mapping
that is parsed from ATAG. Useful for devices that cannot be
safely repartitioned.

Enable via: CONFIG_MTD_SWAP_USERPARTITIONS

Change-Id: Ia0d698c46d31e254b527fe79726891e5ac255fbd
nand_partitions: implement whitelist to write-protect sensitive partitions

Enable via CONFIG_MTD_ANDROID_WHITELIST=y

Change-Id: I284d6302b007021a8131f79160f83471bd79928b
Revert "fs: yaffs2: Revert to older version"

This reverts commit 4c3fda289a8bbb46d4b31867085383ae808d867d.

Testing has shown this change is not necessary on the current
tip.

(cherry picked from commit d5f0c84df23717a67775a4f43f081694a8528708)

Orig-Change-Id: Ic4e93f809eecb9e4cd0c06469da68942a5a79071
Signed-off-by: Michael Bohan <mbohan@codeaurora.org>

Change-Id: I5c1c35cb28d19740dbf230a2a30653e326e338ce