When summing capacities, skip info from batteries that weren't present.

Previously, we used all info (including -1 or "not present") which would
keep the system from reaching 100% when charging.

Reported by:	Eric Anderson
MFC after:	2 days

sys/dev/acpica/acpi_battery.c

@@ -225,6 +225,10 @@ acpi_battery_get_battinfo(device_t dev, struct acpi_battinfo *battinfo)
 	else
 	    bi[i].min = 0;
 	total_min += bi[i].min;
+
+	/* If this battery is not present, don't use its capacity. */
+	if (bi[i].cap == -1)
+	    bi[i].cap = 0;
 	total_cap += bi[i].cap;
     }