ext4: fold ext4_journal_revoke() into ext4_forget()

The only caller of ext4_journal_revoke() is ext4_forget(), so we can
fold ext4_journal_revoke() into ext4_forget() to simplify the code and
shorten the 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