JBD2: replace jbd_kmalloc with kmalloc directly.

This patch cleans up jbd_kmalloc and replace it with kmalloc directly

Signed-off-by: Mingming Cao <cmm@us.ibm.com>

diff --cc fs/jbd2/journal.c
Simple merge

diff --cc fs/jbd2/transaction.c
Simple merge

diff --cc include/linux/jbd2.h
Simple merge