[SCSI] fcoe: Increase FCOE_MAX_LUN to 0xFFFF (65535)

The maximum number of LUNs was far too low. This value is
what most other FC HBAs are using.

Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>