Let's always use the platform device for dev_* and not sometimes the
adapter device as well. Also fix this checkpatch check:

CHECK: Macro argument 'i2c' may be better as '(i2c)' to avoid precedence issues
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Acked-by: Shawn Guo <shawnguo@kernel.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>