fix: ext4: fast commit recovery path (v5.10)

See upstream commit :

  commit 8016e29f4362e285f0f7e38fadc61a5b7bdfdfa2
  Author: Harshad Shirwadkar <harshadshirwadkar@gmail.com>
  Date:   Thu Oct 15 13:37:59 2020 -0700

    ext4: fast commit recovery path

    This patch adds fast commit recovery path support for Ext4 file
    system. We add several helper functions that are similar in spirit to
    e2fsprogs journal recovery path handlers. Example of such functions
    include - a simple block allocator, idempotent block bitmap update
    function etc. Using these routines and the fast commit log in the fast
    commit area, the recovery path (ext4_fc_replay()) performs fast commit
    log recovery.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ia65cf44e108f2df0b458f0d335f33a8f18f50baa