driver core: fw_devlink_flags can be static

Fixes: 8375e74f

 ("driver core: Add fw_devlink kernel commandline option")
Signed-off-by: kbuild test robot <lkp@intel.com>
Acked-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20200305020916.GA14234@3143ef58ba07
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>