nvme: fabrics commands should use the fctype field for data direction

Fabrics commands with opcode 0x7F use the fctype field to indicate data
direction.

Signed-off-by: Jon Derrick <jonathan.derrick@intel.com>
Reviewed-by: Sagi Grimberg <sai@grmberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Fixes: eb793e2c ("nvme.h: add NVMe over Fabrics definitions")