iomap: move iomap_read_inline_data around

iomap_read_inline_data ended up being placed in the middle of the bio
based read I/O completion handling, which tends to confuse the heck out
of me whenever I follow the code.  Move it to a more suitable place.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>