xfs: make inode quota check more general

The xfs checks quota when reserving disk blocks and inodes. In the block
reservation, it checks if the total number of blocks including current
usage and new reservation exceed quota. In the inode reservation,
it checks using the total number of inodes including only current usage
without new reservation. However, this inode quota check works well
since the caller of xfs_trans_dquot() always sets the argument of the
number of new inode reservation to 1 or 0 and inode is reserved one by
one in current xfs.

To make it more general, this patch changes it to the same way as the
block quota check.

Signed-off-by: Mitsuo Hayasaka <mitsuo.hayasaka.hu@hitachi.com>
Cc: Ben Myers <bpm@sgi.com>
Cc: Alex Elder <elder@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ben Myers <bpm@sgi.com>