nvme: Allow to set PRP2

nvme: Allow to set PRP2

When creating a PRP based I/O request, we pass in the pointer to operate
on. Going forward, we will want to be able to pass additional pointers
though for mappings above 4k.

This patch adds a parameter to nvme_get_next_sqe() to pass in the PRP2
value of an NVMe I/O request, paving the way for a future patch to
implement PRP lists.

Signed-off-by: Alexander Graf <graf@amazon.com>
Reviewed-by: Filippo Sironi <sironi@amazon.de>