Allow building without battery charging

Some experimental boards may want to build without a battery charging task
to make bringup easier.

BUG=chrome-os-partner:18343
TEST=build all boards
BRANCH=none

Change-Id: I4269fea4046325241ad7720ec3457b0534aadda3
Signed-off-by: Bill Richardson <wfrichar@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/48974
Reviewed-by: Randall Spangler <rspangler@chromium.org>

chip/lm4/switch.c

@@ -373,8 +373,10 @@ static void state_machine(uint64_t tnow)
 		 * Otherwise we could power on the AP only to shut it right
 		 * back down due to insufficient battery.
 		 */
+#ifdef CONFIG_TASK_CHARGER
 		if (charge_get_state() == PWR_STATE_INIT)
 			break;
+#endif
 
 		/*
 		 * Power the system on if possible.  Gating due to insufficient

include/charge_state.h

@@ -146,7 +146,10 @@ int charge_get_percent(void);
 /**
  * Return non-zero if discharging and battery so low we should shut down.
  */
+#ifdef CONFIG_TASK_CHARGER
 int charge_want_shutdown(void);
-
+#else
+static inline int charge_want_shutdown(void) { return 0; }
+#endif
 #endif /* __CROS_EC_CHARGE_STATE_H */