ext4: return non-zero st_blocks for inline data

Return a non-zero st_blocks to userspace for statfs() and friends.
Some versions of tar will assume that files with st_blocks == 0
do not contain any data and will skip reading them entirely.

Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>