xfs: replace xfs_bmbt_lookup_ge with xfs_bmbt_lookup_first

xfs: replace xfs_bmbt_lookup_ge with xfs_bmbt_lookup_first

Source kernel commit: b5cfbc2282bcd0dba460d4d4ec07fcfac9981de6

We only use xfs_bmbt_lookup_ge to look up the first bmap record in an
inode, so replace xfs_bmbt_lookup_ge with a special purpose helper that
is a bit more descriptive.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>