dell_rbu: Select CONFIG_FW_LOADER_USER_HELPER explicitly

The usermode helper is mandatory for this driver.
Signed-off-by: NTakashi Iwai <tiwai@suse.de>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/firmware/Kconfig

@@ -64,6 +64,7 @@ config DELL_RBU
 	tristate "BIOS update support for DELL systems via sysfs"
 	depends on X86
 	select FW_LOADER
+	select FW_LOADER_USER_HELPER
 	help
 	 Say m if you want to have the option of updating the BIOS for your
 	 DELL system. Note you need a Dell OpenManage or Dell Update package (DUP)