ext4: add a function which sets up group blocks of a flex bg

This patch adds a function named setup_new_flex_group_blocks() which
sets up group blocks of a flex bg.

Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

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

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