Replace all occurences of sprintf with snprintf

THis reduces risks of bufer overflows.

Change-Id: I77f80e76efec16ac0a0af83d76430a8126a7602d
Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
Reviewed-on: http://review.coreboot.org/4279
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

src/mainboard/intel/wtm2/i915.c

@@ -88,7 +88,7 @@ static int ioread = 0, iowrite = 0;
 static char *regname(unsigned long addr)
 {
 	static char name[16];
-	sprintf(name, "0x%lx", addr);
+	snprintf(name, sizeof (name), "0x%lx", addr);
 	return name;
 }