scsi: fcoe: fix build error

I had a typo in a variable name for the previous patch (SCSI: fcoe:
convert bus code to use bus_group) that broke the build, this fixes
that.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>