i2c: Change prototypes of refcounting functions

Use more standard prototypes for i2c_use_client() and
i2c_release_client(). The former now returns a pointer to the client,
and the latter no longer returns anything. This matches what all other
subsystems do.

Signed-off-by: Jean Delvare <[email protected]>
Cc: David Brownell <[email protected]>
3 files changed