ext4: add ext4_sb_block_valid() refactored out of ext4_inode_block_valid()

commit 6bc6c2bd upstream.

This API will be needed at places where we don't have an inode
for e.g. while freeing blocks in ext4_group_add_blocks()

Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Ritesh Harjani <riteshh@linux.ibm.com>
Link: https://lore.kernel.org/r/dd34a236543ad5ae7123eeebe0cb69e6bdd44f34.1644992610.git.riteshh@linux.ibm.com


Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>