hw/i2c: add match method for device search

hw/i2c: add match method for device search

At the start of an i2c transaction, the i2c bus searches its list of
children to identify which devices correspond to the address (or
broadcast).  Now the I2CSlave device has a method "match" that
encapsulates the lookup behavior. This allows the behavior to be changed
to support devices, such as i2c muxes.

Tested: A BMC firmware was booted to userspace and i2c devices were
detected.

Signed-off-by: Patrick Venture <venture@google.com>
Reviewed-by: Hao Wu <wuhaotsh@google.com>
Message-Id: <20210412194522.664594-3-venture@google.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>