firmware loader: fix build failure with !CONFIG_FW_LOADER_USER_HELPER

This patch fixes one build failure which is introduced by the patch
below:

	driver core: firmware loader: kill FW_ACTION_NOHOTPLUG requests
	before suspend

When CONFIG_FW_LOADER_USER_HELPER is unset, kill_requests_without_uevent()
should be nop because no userspace loading is involved.

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