i2c: versatile: Convert to use resource managed devm_* APIs

Use devm_* APIs to simplify the code a bit.
This patch also fixes the memory leak when unload the module.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Tested-by: Liviu Dudau <Liviu.Dudau@arm.com>
Acked-by: Liviu Dudau <Liviu.Dudau@arm.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>