xfs: remove usage of is_bad_inode

XFS never calls mark_inode_bad or iget_failed, so it will never see a
bad inode.  Remove all checks for is_bad_inode because they are
unnecessary.

Signed-off-by: Ben Myers <bpm@sgi.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

diff --cc fs/xfs/xfs_icache.c
Simple merge

diff --cc fs/xfs/xfs_inode.c
Simple merge

diff --cc fs/xfs/xfs_super.c
Simple merge