evbarm/generic_v5: fix setstatclockrate crash

setstatclockrate is an optional function for timers that currently cannot be multiplexed through device trees. We don't provide an implementation in the am18 code, but we need to make sure the imx23 driver doesn't crash us.

Author: recursivetree

sys/arch/arm/imx/imx23_timrot.c

@@ -78,7 +78,7 @@ static const struct device_compatible_entry compat_data[] = {
 	DEVICE_COMPAT_EOL
 };
 
-static struct imx23_timrot_softc *timer_sc;
+static struct imx23_timrot_softc *timer_sc = NULL;
 
 #define TIMROT_SOFT_RST_LOOP 455 /* At least 1 us ... */
 #define TIMROT_READ(sc, reg)						\
@@ -197,9 +197,11 @@ setstatclockrate(int newhz)
 {
 	struct imx23_timrot_softc *sc = timer_sc;
 
-	TIMER_WRITE_2(sc, HW_TIMROT_TIMCOUNT1,
-		      __SHIFTIN(SOURCE_32KHZ_HZ / newhz - 1,
-				HW_TIMROT_TIMCOUNT1_FIXED_COUNT));
+	if(sc != NULL) {
+		TIMER_WRITE_2(sc, HW_TIMROT_TIMCOUNT1,
+			      __SHIFTIN(SOURCE_32KHZ_HZ / newhz - 1,
+					HW_TIMROT_TIMCOUNT1_FIXED_COUNT));
+	}
 }
 
 /*