ext4: fix block validity checks so they work correctly with meta_bg

The block validity checks used by ext4_data_block_valid() wasn't
correctly written to check file systems with the meta_bg feature.  Fix
this.

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

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

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