ARM: dts: aspeed: Add ASRock ROMED8HM3 BMC

This is a half-width, single-socket Epyc server board with an AST2500
BMC.  This device tree is sufficient for basic OpenBMC functionality,
but we'll need to add a few more devices (as driver support becomes
available) before it's fully usable.

Signed-off-by: Zev Weiss <zev@bewilderbeest.net>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Link: https://lore.kernel.org/r/20220105101719.7093-1-zev@bewilderbeest.net
Signed-off-by: Joel Stanley <joel@jms.id.au>