NVMe: small typo in section BLK_DEV_NVME_SCSI of host/Kconfig

"as well as " is miss typed "as well a " in section
"config BLK_DEV_NVME_SCSI"

Signed-off-by: Wang Sheng-Hui <shhuiw@foxmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>