aspeed: Add support for the sonorapass-bmc board

aspeed: Add support for the sonorapass-bmc board

Sonora Pass is a 2 socket x86 motherboard designed by Facebook
and supported by OpenBMC.  Strapping configuration was obtained
from hardware and i2c configuration is based on dts found at:

https://github.com/facebook/openbmc-linux/blob/1633c87b8ba7c162095787c988979b748ba65dc8/arch/arm/boot/dts/aspeed-bmc-facebook-sonorapass.dts

Booted a test image of http://github.com/facebook/openbmc to login
prompt.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Reviewed-by: Amithash Prasad <amithash@fb.com>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
[PMM: fixed block comment style nit]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>