[SCSI] libfc: fix payload size passed to fc_frame_alloc() in fc_lport_els_request

Frame header room is already incluced, just pass the length of payload.

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