ixgbe: Fix format string in ixgbe_fcoe.

cppcheck detected following warning in ixgbe_fcoe.c (warning) %d in format
string (no. 1) requires 'int' but the argument type is 'unsigned int'.

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Tested-By: Jack Morgan <jack.morgan@intel.com>
Signed-off-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>