[PATCH] bs= and bsrange= takes both read and write sizes

[PATCH] bs= and bsrange= takes both read and write sizes

Get rid of read_bs/write_bs and read_bsrange/write_bsrange. It was ugly
and too complicated. Instead support giving both values in a single bs=
or bsrange= seperated by a comma.

Example: bs=1k,4k will use 1k blocks for reads, 4k blocks for writes.
	 bs=32k will use 32k blocks for both reads and writes.

Similar for bsrange=

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>