Reliably autodetect battery device in statusbar

Wireless devices have "Wireless" type, so we search for nodes with type
"Battery". We also may handle wireless devices that way, if anyone needs
that.

Signed-off-by: Stacy Harper <contact@stacyharper.net>

scripts/core/sxmo_statusbar.sh

@@ -54,12 +54,14 @@ update() {
 		fi
 	fi
 
-	# Battery pct
-	BATTERY_DEVICE="${BATTERY_DEVICE:-"/sys/class/power_supply/axp20x-battery"}"
-	PCT="$(cat "$BATTERY_DEVICE"/capacity)"
-	BATSTATUS="$(
-		cut -c1 "$BATTERY_DEVICE"/status
-	)"
+	# Find battery and get percentage + status
+	for power_supply in /sys/class/power_supply/*; do
+		if [ "$(cat "$power_supply"/type)" = "Battery" ]; then
+			PCT="$(cat "$power_supply"/capacity)"
+			BATSTATUS="$(cut -c1 "$power_supply"/status)"
+		fi
+	done
+
 	if [ "$BATSTATUS" = "C" ]; then
 		if [ "$PCT" -lt 20 ]; then
 			BATSTATUS="$PCT% "