hw/i2c/aspeed_i2c: Simplify aspeed_i2c_get_bus()

hw/i2c/aspeed_i2c: Simplify aspeed_i2c_get_bus()

All the callers of aspeed_i2c_get_bus() have a AspeedI2CState and
cast it to a DeviceState with DEVICE(), then aspeed_i2c_get_bus()
cast the DeviceState to an AspeedI2CState with ASPEED_I2C()...

Simplify aspeed_i2c_get_bus() callers by using AspeedI2CState
argument.

Reviewed-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Andrew Jeffery <andrew@aj.id.au>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20200705224154.16917-2-f4bug@amsat.org>
Signed-off-by: Corey Minyard <cminyard@mvista.com>