[SCSI] fcoe: fix missing error check in call to fcoe_if_init

fcoe_if_init() can fail, but it's return value wasn't checked

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