hw/mc146818: Drop unneeded #includes

pc.h and apic.h are not needed; apic.h would drag in x86 CPUState and
is now included directly for TARGET_I386.

isa.h is already #included from mc146818rtc.h.
Signed-off-by: NAndreas Färber <afaerber@suse.de>
Reviewed-by: NAnthony Liguori <aliguori@us.ibm.com>

hw/mc146818rtc.c

@@ -24,8 +24,6 @@
 #include "hw.h"
 #include "qemu-timer.h"
 #include "sysemu.h"
-#include "pc.h"
-#include "isa.h"
 #include "mc146818rtc.h"
 
 #ifdef TARGET_I386