cpu: Convert the methods to use a const udevice *

These functions should not modify the device. Convert them to const so
that callers don't need to cast if they have a const udevice *.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/cpu/bmips_cpu.c b/drivers/cpu/bmips_cpu.c
index 2649c5c..421cc7a 100644
--- a/drivers/cpu/bmips_cpu.c
+++ b/drivers/cpu/bmips_cpu.c
@@ -379,7 +379,7 @@
 };
 
 /* Generic CPU Ops */
-static int bmips_cpu_get_desc(struct udevice *dev, char *buf, int size)
+static int bmips_cpu_get_desc(const struct udevice *dev, char *buf, int size)
 {
 	struct bmips_cpu_priv *priv = dev_get_priv(dev);
 	const struct bmips_cpu_hw *hw = priv->hw;
@@ -387,7 +387,7 @@
 	return hw->get_cpu_desc(priv, buf, size);
 }
 
-static int bmips_cpu_get_info(struct udevice *dev, struct cpu_info *info)
+static int bmips_cpu_get_info(const struct udevice *dev, struct cpu_info *info)
 {
 	struct bmips_cpu_priv *priv = dev_get_priv(dev);
 	const struct bmips_cpu_hw *hw = priv->hw;
@@ -400,7 +400,7 @@
 	return 0;
 }
 
-static int bmips_cpu_get_count(struct udevice *dev)
+static int bmips_cpu_get_count(const struct udevice *dev)
 {
 	struct bmips_cpu_priv *priv = dev_get_priv(dev);
 	const struct bmips_cpu_hw *hw = priv->hw;
@@ -408,7 +408,7 @@
 	return hw->get_cpu_count(priv);
 }
 
-static int bmips_cpu_get_vendor(struct udevice *dev, char *buf, int size)
+static int bmips_cpu_get_vendor(const struct udevice *dev, char *buf, int size)
 {
 	snprintf(buf, size, "Broadcom");