iomap: Add IOMAP_F_DATA_INLINE flag

Add a new IOMAP_F_DATA_INLINE flag to indicate that a mapping is in a
disk area that contains data as well as metadata.  In iomap_fiemap, map
this flag to FIEMAP_EXTENT_DATA_INLINE.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>