i2c: move locking operations to their own struct

This makes it trivial to constify them, so do that.

Signed-off-by: Peter Rosin <peda@axentia.se>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
4 files changed