i2c: Change the type of the data parameter to uint8_t.

Data is intended to be a byte array, so it should be described by a type which
has a fixed size equal to an 8 bit byte. Also, the data passed to write
shouldn't be modified and can be const.

Change-Id: I6466303d962998f6c37c2d4006a39c2d79a235c1
Signed-off-by: Gabe Black <gabeblack@chromium.org>
Reviewed-on: http://review.coreboot.org/3721
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
diff --git a/src/include/device/i2c.h b/src/include/device/i2c.h
index d880a7b..997d201 100644
--- a/src/include/device/i2c.h
+++ b/src/include/device/i2c.h
@@ -20,10 +20,12 @@
 #ifndef _DEVICE_I2C_H_
 #define _DEVICE_I2C_H_
 
+#include <stdint.h>
+
 /* note: chip is the 7-bit I2C address */
 int i2c_read(unsigned bus, unsigned chip, unsigned addr,
-		unsigned alen, unsigned char *buf, unsigned len);
+		unsigned alen, uint8_t *buf, unsigned len);
 int i2c_write(unsigned bus, unsigned chip, unsigned addr,
-		unsigned alen, unsigned char *buf, unsigned len);
+		unsigned alen, const uint8_t *buf, unsigned len);
 
 #endif	/* _DEVICE_I2C_H_ */