Sqrt function for Cortex-M

Add an arch include folder. Implement sqrtf for Cortex-M in math.h.

BUG=chrome-os-partner:7920
TEST=none

Change-Id: Ib7b480b6a0bf7760f014a1f73df54673a9016cb6
Signed-off-by: Vic Yang <victoryang@chromium.org>

Makefile

@@ -43,6 +43,6 @@ all-y+=$(call objs_from_dir,board/$(BOARD),$(board-y))
 all-y+=$(call objs_from_dir,common,$(common-y))
 all-y+=$(call objs_from_dir,test,$($(PROJECT)-y))
 dirs=core/$(CORE) chip/$(CHIP) board/$(BOARD) common test util
-includes=include $(dirs)
+includes=include core/$(CORE)/include $(dirs)
 
 include Makefile.rules

core/cortex-m/include/math.h

@@ -0,0 +1,24 @@
+/* Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+/* Math utility functions for ARMv7 */
+
+#ifndef __EC_MATH_H
+#define __EC_MATH_H
+
+#ifdef CONFIG_FPU
+static inline float sqrtf(float v)
+{
+	float root;
+	asm volatile(
+		"fsqrts %0, %1"
+		: "=w" (root)
+		: "w" (v)
+	);
+	return root;
+}
+#endif  /* CONFIG_FPU */
+
+#endif  /* __EC_MATH_H */