libqos: i2c: move address into QI2CDevice

This removes the hardcoded I2C address from the tests.  The address
is passed via QOSGraphEdgeOptions to i2c_device_create and stored
in the QI2CDevice.

The i2c_send and i2c_recv functions, along with their wrappers,
therefore, can be changed to take a QI2CDevice rather than an
adapter/address pair.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>