remove some double-includes

Some source files #include the same header more than
once for no good reason.  Remove second #includes in
such cases.

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

hw/timer/exynos4210_rtc.c

@@ -31,7 +31,6 @@
 #include "hw/ptimer.h"
 
 #include "hw/hw.h"
-#include "qemu/timer.h"
 #include "sysemu/sysemu.h"
 
 #include "hw/arm/exynos4210.h"