sd: fix a bug in deriving the FLUSH_TIMEOUT from the basic I/O timeout

Commit ID: 7e660100 added code to derive the
FLUSH_TIMEOUT from the basic I/O timeout. However, this patch did not use the
basic I/O timeout of the device. Fix this bug.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: James Bottomley <JBottomley@Parallels.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>