HID: steam: select CONFIG_POWER_SUPPLY

Using the power supply APIs requires selecting the appropriate
Kconfig symbol, otherwise we get this build failure:

drivers/hid/hid-steam.o: In function `steam_unregister':
hid-steam.c:(.text+0x1cc): undefined reference to `power_supply_unregister'
drivers/hid/hid-steam.o: In function `steam_battery_get_property':
hid-steam.c:(.text+0x2d2): undefined reference to `power_supply_get_drvdata'
drivers/hid/hid-steam.o: In function `steam_raw_event':
hid-steam.c:(.text+0xcba): undefined reference to `power_supply_changed'
drivers/hid/hid-steam.o: In function `steam_register':
hid-steam.c:(.text+0x13e3): undefined reference to `power_supply_register'
hid-steam.c:(.text+0x13fe): undefined reference to `power_supply_powers'

Fixes: f8271979 ("HID: steam: add battery device.")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/Kconfig

@@ -841,6 +841,7 @@ config HID_SPEEDLINK
 config HID_STEAM
 	tristate "Steam Controller support"
 	depends on HID
+	select POWER_SUPPLY
 	---help---
 	Say Y here if you have a Steam Controller if you want to use it
 	without running the Steam Client. It supports both the wired and