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 <clg@kaod.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Corey Minyard <cminyard@mvista.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Tested-by: Cédric Le Goater <clg@kaod.org>
Message-id: 20200623072723.6324-8-f4bug@amsat.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>