nvme-fc: remove NVME_FC_MAX_SEGMENTS

The define is an arbitrary limit to the io size on the initiator,
capping the io to 1MB-4KB.

Remove the define from the transport. I/O size will solely be limited
by the LLDD sg limits.

Signed-off-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>