Compile qemu-timer only once

Arrange various declarations so that also non-CPU code can access
them, adjust users.

Move CPU specific code to cpus.c.

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
diff --git a/translate-all.c b/translate-all.c
index 8ef8a0b..6f8136b 100644
--- a/translate-all.c
+++ b/translate-all.c
@@ -29,6 +29,7 @@
 #include "exec-all.h"
 #include "disas.h"
 #include "tcg.h"
+#include "qemu-timer.h"
 
 /* code generation context */
 TCGContext tcg_ctx;