hw/arm/aspeed: Describe each PCA9552 device

hw/arm/aspeed: Describe each PCA9552 device

We have 2 distinct PCA9552 devices. Set their description
to distinguish them when looking at the trace events.

Description name taken from:
https://github.com/open-power/witherspoon-xml/blob/master/witherspoon.xml

Reviewed-by: Cédric Le Goater <[email protected]>
Signed-off-by: Philippe Mathieu-Daudé <[email protected]>
Reviewed-by: Corey Minyard <[email protected]>
Reviewed-by: Markus Armbruster <[email protected]>
Tested-by: Cédric Le Goater <[email protected]>
Message-id: 20200623072723[email protected]
Signed-off-by: Peter Maydell <[email protected]>