ARM: dts: aspeed: Enable ADC in Facebook AST2400 common dtsi

Enable ADC controller in "ast2400-facebook-netbmc-common.dtsi" because
the device is used on all the Facebook AST2400 BMC platforms.

Signed-off-by: Tao Ren <rentao.bupt@gmail.com>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Link: https://lore.kernel.org/r/20210719001724.6410-2-rentao.bupt@gmail.com


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