from richard / bls: set maximum frequency

Reference: /n/atom/patch/applied/piicanhazturboz
Date: Mon Jan  4 16:25:40 CET 2016
Signed-off-by: quanstro@quanstro.net

--- /sys/src/9/bcm/main.c	Mon Jan  4 16:24:14 2016
+++ /sys/src/9/bcm/main.c	Mon Jan  4 16:24:15 2016
@@ -3,6 +3,7 @@
 #include "../port/lib.h"
 #include "mem.h"
 #include "dat.h"
+#include "io.h"
 #include "fns.h"
 
 #include "init.h"
@@ -349,6 +350,8 @@
 		for(;;)
 			;
 	}
+	/* set clock rate to arm_freq from config.txt (default pi1:700Mhz pi2:900MHz) */
+	setclkrate(ClkArm, 0);
 	trapinit();
 	clockinit();
 	printinit();