blkg_rwstat: separate op from flags

blkg_rwstat: separate op from flags

The bio and request operation and flags are going to be separate
definitions, so we cannot pass them in as a bitmap. This patch
converts the blkg_rwstat code and its caller, cfq, to pass in the
values separately.

Signed-off-by: Mike Christie <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>