ext4: fold ext4_journal_forget() into ext4_forget()

Convert the last two callers of ext4_journal_forget() to use
ext4_forget() instead, and then fold ext4_journal_forget() into
ext4_forget().  This reduces are code complexity and shortens our call
stack.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --cc fs/ext4/ext4_jbd2.c
Simple merge

diff --cc fs/ext4/ext4_jbd2.h
Simple merge

diff --cc fs/ext4/inode.c
Simple merge