Documentation/i2c: adopt kernel commenting style in examples

The example I2C code is rewritten to adopt the preferred kernel block
commenting style.
Signed-off-by: NSam Hansen <hansens@google.com>
Signed-off-by: NWolfram Sang <wsa@the-dreams.de>

Documentation/i2c/dev-interface

@@ -67,8 +67,10 @@ the device supports them. Both are illustrated below.
     /* res contains the read word */
   }
 
-  /* Using I2C Write, equivalent of
-     i2c_smbus_write_word_data(file, reg, 0x6543) */
+  /*
+   * Using I2C Write, equivalent of
+   * i2c_smbus_write_word_data(file, reg, 0x6543)
+   */
   buf[0] = reg;
   buf[1] = 0x43;
   buf[2] = 0x65;