nvme: centralize setting the timeout in nvme_alloc_request

The function nvme_alloc_request() is called from different context
(I/O and Admin queue) where callers do not consider the I/O timeout when
called from I/O queue context.

Update nvme_alloc_request() to set the default I/O and Admin timeout
value based on whether the queuedata is set or not.

Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>