xfs: always free inline data before resetting inode fork during ifree

In xfs_ifree, we reset the data/attr forks to extents format without
bothering to free any inline data buffer that might still be around
after all the blocks have been truncated off the file.  Prior to commit
43518812 ("xfs: remove support for inlining data/extents into the
inode fork") nobody noticed because the leftover inline data after
truncation was small enough to fit inside the inline buffer inside the
fork itself.

However, now that we've removed the inline buffer, we /always/ have to
free the inline data buffer or else we leak them like crazy.  This test
was found by turning on kmemleak for generic/001 or generic/388.

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