[SCSI] libfc: introduce __fc_fill_fc_hdr that accepts fc_hdr as an argument

fc_fill_fc_hdr() expects fc_frame as an argument. Introduce __fc_fill_fc_hdr to
accept fc_frame_header as an argument.

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