f2fs support

fusion of multiples commits of andi34 kernel:
- https://github.com/andi34/android_kernel_samsung_golden/commit/76bb3508e61ab01948e5df2de1c1c105be8d60b4
- https://github.com/andi34/android_kernel_samsung_golden/commit/50ee8aeed7a99223f0930b2f0f74cefd5d41327e
- https://github.com/andi34/android_kernel_samsung_golden/commit/687026933d3ac563b03e81602cb94ee4a9069499
- https://github.com/andi34/android_kernel_samsung_golden/commit/4ae0e76118d174c3e5cf504152e9a689891fc3e1
- https://github.com/andi34/android_kernel_samsung_golden/commit/ff245085877b48c3b5efecf190fd61567b5b93cf
- https://github.com/andi34/android_kernel_samsung_golden/commit/eba1141793b4f0c39c0c480158037d0bbd0a2e4f
- https://github.com/andi34/android_kernel_samsung_golden/commit/f3e45a35098c1b75eb49cebfa9108a9a4bbd10b8
- https://github.com/andi34/android_kernel_samsung_golden/commit/3f68f0ef51ed2b1583ea1cbbc78a583983c8f74b
- https://github.com/andi34/android_kernel_samsung_golden/commit/553093b86035924cbede9763d1b44550df05b76f
- https://github.com/andi34/android_kernel_samsung_golden/commit/30fe46687b6a10e740c5f5d4c43d78ef63789d81
- https://github.com/andi34/android_kernel_samsung_golden/commit/b684e4fd23ab23ccba4c8460046ed81e9fb969aa
- https://github.com/andi34/android_kernel_samsung_golden/commit/559855d04b96400c710a8d384fdebecdde98da2c
- https://github.com/andi34/android_kernel_samsung_golden/commit/c14cafbc6a24433b0a0f59ce2906d8c38691dcd5
- https://github.com/andi34/android_kernel_samsung_golden/commit/461f4205c509981d7afce8790edad7f3b795df99
- https://github.com/andi34/android_kernel_samsung_golden/commit/ac952c2cb056274a194e7d020b75d95ad14852e8
- https://github.com/andi34/android_kernel_samsung_golden/commit/616cde8813d15447d347d545d396d30aafd92d37
- https://github.com/andi34/android_kernel_samsung_golden/commit/714fb8a589e7ec93bcfa784d046137579270fdf6
- https://github.com/andi34/android_kernel_samsung_golden/commit/535e2497c4c219c548d8279c74b7bcf2b13d9fbc
- https://github.com/andi34/android_kernel_samsung_golden/commit/44c7ed04394eb8d3403efb7467dbcb71da56c6cb
defconfig: enable F2FS Filesystem support
block: separate priority boosting from REQ_META

Add a new REQ_PRIO to let requests preempt others in the cfq I/O schedule,
and lave REQ_META purely for marking requests as metadata in blktrace.

All existing callers of REQ_META except for XFS are updated to also
set REQ_PRIO for now.

Backported to 3.0.101 by Ketut Putu Kumajaya <ketut.kumajaya@gmail.com>