xfs: Fix error code in 'xfs_ioc_getbmap()'

xfs: Fix error code in 'xfs_ioc_getbmap()'

In this function, once 'buf' has been allocated, we unconditionally
return 0.
However, 'error' is set to some error codes in several error handling
paths.
Before commit 29a3e8cd9447 ("xfs: simplify the xfs_getbmap interface")
this was not an issue because all error paths were returning directly,
but now that some cleanup at the end may be needed, we must propagate the
error code.

Fixes: 29a3e8cd9447 ("xfs: simplify the xfs_getbmap interface")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>