ARM: dts: aspeed: cloudripper: Add comments for "mdio1"

Add some comments to explain the purpose of "mdio1" controller: it's
connected to the MDC/MDIO interface of the on-board management switch.

Signed-off-by: Tao Ren <rentao.bupt@gmail.com>
Link: https://lore.kernel.org/r/20210813061900.24539-1-rentao.bupt@gmail.com


Signed-off-by: Joel Stanley <joel@jms.id.au>