xfs: rename xfs_*alloc*_log_count to _block_count

xfs: rename xfs_*alloc*_log_count to _block_count

Source kernel commit: 6ed7e509d2304519f4f6741670f512a55e9e80fe

These functions return the maximum number of blocks that could be logged
in a particular transaction.  "log count" is confusing since there's a
separate concept of a log (operation) count in the reservation code, so
let's change it to "block count" to be less confusing.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>