ARM: dts: aspeed-g4: add vhub port and endpoint properties

Add "aspeed,vhub-downstream-ports" and "aspeed,vhub-generic-endpoints"
properties to describe supported number of vhub ports and endpoints.

Signed-off-by: Tao Ren <rentao.bupt@gmail.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Felipe Balbi <balbi@kernel.org>