i2c: Implement open and close

Implement open() and close() function, and invoke open() on creating
I2CDevice, and invoke close() in destructor.

Tested: Manually write test codet and run on Witherspoon that it opens
        and closes the i2c device correctly.

Signed-off-by: Lei YU <mine260309@gmail.com>
Change-Id: I709fcc80474a4a0cef067748a78256ceb76430a5
diff --git a/tools/i2c/meson.build b/tools/i2c/meson.build
index 1f4e7d1..258ac77 100644
--- a/tools/i2c/meson.build
+++ b/tools/i2c/meson.build
@@ -3,3 +3,5 @@
     'i2c.cpp',
     link_args : '-li2c',
 )
+
+libi2c_inc = include_directories('.')