i2c: Implement write function

Implement I2CDevice::write() by invoking i2c_smbus_write_xxx() APIs.
The code is referenced from i2c-tools' i2cset.c:

 https://github.com/ev3dev/i2c-tools/blob/ev3dev-stretch/tools/i2cset.c

Tested: Verify on Witherspoon that it writes the PSU unlock upgrade
        command and boot flag successfully.

Signed-off-by: Lei YU <mine260309@gmail.com>
Change-Id: I9fb014c787ef3ebb2f7793a0d012b1d652ef069f
diff --git a/tools/i2c/i2c.hpp b/tools/i2c/i2c.hpp
index 7fe064f..befeaba 100644
--- a/tools/i2c/i2c.hpp
+++ b/tools/i2c/i2c.hpp
@@ -53,6 +53,17 @@
      */
     void checkReadFuncs(int type);
 
+    /** @brief Check i2c adapter write functionality
+     *
+     * Check if the i2c adapter has the functionality specified by the SMBus
+     * transaction type
+     *
+     * @param[in] type - The SMBus transaction type defined in linux/i2c.h
+     *
+     * @throw I2CException if the function is not supported
+     */
+    void checkWriteFuncs(int type);
+
   public:
     ~I2CDevice()
     {