Remove code dealing with negative sector numbers for byte access in
bdrv_check_request as sector numbers can't ever be negative.

Previously we supported negative sector counts for byte access, but
never sector numbers.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>


git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6942 c046a42c-6fe2-441c-8c8c-71466251a162