Stop calling atrtc_set() from the xen timer clock_settime() method. That

removes the only reference to atrtc_set() from outside of atrtc.c, so make
it static.

The xen timer driver registers as a realtime clock with 1us resolution.  In
the past that resulted in only the xen timer's clock_settime() getting
called, so it would call atrtc_set() to set the hardware clock as well.  As
of r32090, the clock_settime() method of all registered realtime clocks gets
called, so the xen driver no longer needs to chain-call the lower-resolution
driver.

Thanks to royger@ for talking me through the xen stuff, and for testing.

sys/dev/xen/timer/timer.c

@@ -64,8 +64,6 @@ __FBSDID("$FreeBSD$");
 
 #include <dev/xen/timer/timer.h>
 
-#include <isa/rtc.h>
-
 #include "clock_if.h"
 
 static devclass_t xentimer_devclass;
@@ -229,9 +227,6 @@ xentimer_settime(device_t dev __unused, struct timespec *ts)
 	if (!xen_initial_domain())
 		return (0);
 
-	/* Set the native RTC. */
-	atrtc_set(ts);
-
 	settime.cmd = XENPF_settime64;
 	settime.u.settime64.mbz = 0;
 	settime.u.settime64.secs = ts->tv_sec;

sys/isa/rtc.h

@@ -118,7 +118,6 @@ extern	int atrtcclock_disable;
 int	rtcin(int reg);
 void	atrtc_restore(void);
 void	writertc(int reg, u_char val);
-void	atrtc_set(struct timespec *ts);
 #endif
 
 #endif /* _I386_ISA_RTC_H_ */

sys/x86/isa/atrtc.c

@@ -164,7 +164,7 @@ atrtc_restore(void)
 	rtcin(RTC_INTR);
 }
 
-void
+static void
 atrtc_set(struct timespec *ts)
 {
 	struct clocktime ct;