memstick: mspro_block: Fix an error code in mspro_block_issue_req()

We accidentally changed the error code from -EAGAIN to 1 when we did the
blk-mq conversion.

Maybe a contributing factor to this mistake is that it wasn't obvious
that the "while (chunk) {" condition is always true.  I have cleaned
that up as well.

Fixes: d0be1227 ("mspro_block: convert to blk-mq")
Cc: stable@vger.kernel.org
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>