hw/arm/mps2.c: Mark internal-only I2C buses as 'full'

hw/arm/mps2.c: Mark internal-only I2C buses as 'full'

The various MPS2 boards implemented in mps2.c have multiple I2C
buses: a bus dedicated to the audio configuration, one for the LCD
touchscreen controller, and two which are connected to the external
Shield expansion connector.  Mark the buses which are used only for
board-internal devices as 'full' so that if the user creates i2c
devices on the commandline without specifying a bus name then they
will be connected to the I2C controller used for the Shield
connector, where guest software will expect them.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20210903151435.22379-5-peter.maydell@linaro.org