ext4: add correct group descriptors and reserved GDT blocks to system zone

ext4: add correct group descriptors and reserved GDT blocks to system zone

commit 68228da51c9a436872a4ef4b5a7692e29f7e5bc7 upstream.

When setup_system_zone, flex_bg is not initialized so it is always 1.
Use a new helper function, ext4_num_base_meta_blocks() which does not
depend on sbi->s_log_groups_per_flex being initialized.

[ Squashed two patches in the Link URL's below together into a single
  commit, which is simpler to review/understand.  Also fix checkpatch
  warnings. --TYT ]

Cc: stable@kernel.org
Signed-off-by: Wang Jianjian <wangjianjian0@foxmail.com>
Link: https://lore.kernel.org/r/tencent_21AF0D446A9916ED5C51492CC6C9A0A77B05@qq.com
Link: https://lore.kernel.org/r/tencent_D744D1450CC169AEA77FCF0A64719909ED05@qq.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>