increments the reference count of the i2c client structure
struct i2c_client * i2c_use_client (
|struct i2c_client * client|
the client being referenced
Each live reference to a client should be refcounted. The driver model does
that automatically as part of driver binding, so that most drivers don't
need to do this explicitly
they hold a reference until they're unbound
from the device.
A pointer to the client with the incremented reference counter is returned.