[ANDROID] f2fs: Set the bio REQ_NOENCRYPT flag

When lower layers such as dm-crypt observe the REQ_NOENCRYPT flag, it
helps the I/O stack avoid redundant encryption, improving performance
and power utilization.

Note that lower layers must be consistent in their observation of this
flag in order to avoid the possibility of data corruption.

Change-Id: I8cea62922dd41ac860d9bad787774aa32115d0b0
Signed-off-by: Michael Halcrow <mhalcrow@google.com>
Git-repo: https://android.googlesource.com/kernel/common


[bmuthuku@codeaurora.org: resolved trivial merge conflicts]
Signed-off-by: Barani Muthukumaran <bmuthuku@codeaurora.org>