ARM: dts: aspeed: mtmitchell: Enable NCSI

ARM: dts: aspeed: mtmitchell: Enable NCSI

Use MAC3 (RGMII4) with the NC-SI stack instead of as an MDIO PHY.

The OCP slot #0 and OCP slot #1 use a common BMC_NCSI signal, so we use
only one of them at a time. The OCP slot #0 will be enabled by PCA9539's
setting by default.

Enable the OCP Auxiliary Power during booting to make the NCSI feature
work.

Signed-off-by: Chanh Nguyen <chanh@os.amperecomputing.com>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Link: https://lore.kernel.org/r/20230228102820.18477-1-chanh@os.amperecomputing.com
Signed-off-by: Joel Stanley <joel@jms.id.au>