matching design doc on blk and its code

[erichchan999]

Currently the design document for storage devices in Listing 5.1 does not match the code. These need to be changed:

• removing count and address fields in blk_response. These were included to simplify the bookkeeping process, and as we implement the various blk components have found them unneccessary.
• QUEUE_SIZE is defined separately for both queues -> BLK_REQ_QUEUE_SIZE, BLK_RESP_QUEUE_SIZE
• The response enum is called a response_status, and is defined separately from the response struct

In Listing 5.2 outlining blk storage information fields:

• an additional sector_size field is added to communicate the minimum blocksize, this may be smaller than the transfer size and will require a different implementation.
• blocksize renamed to block_size for consistency
• additional comments

[Ivan-Velickovic]

Also, the head and tail indices seem to be reversed compared to the network queue.