libfc, fcoe, bnx2fc: Always use fcoe_disc_init for discovery layer initialization

Currently libfcoe is doing some libfc discovery layer initialization outside of
libfc. This patch moves this code into libfc and sets up a split in discovery
(one time) initialization code and (re-configurable) settings that will come in
the next patch.

Signed-off-by: Robert Love <robert.w.love@intel.com>
Tested-by: Jack Morgan <jack.morgan@intel.com>
Reviewed-by: Bhanu Prakash Gollapudi <bprakash@broadcom.com>