ARM: dts: aspeed: Set earlycon boot argument

Most of the aspeed boards have copied the 'earlyprink' string in
the bootargs. However, there's no earlyprink driver configured in the
defconfigs, so this does nothing.

A combination of setting stdout in the chosen node and adding earlycon
to bootargs causes early serial output to appear early. This changes all
boards to use this option.

The console=ttyS4,115200 option is still required, as this is used by
the run time uart driver.

Signed-off-by: Joel Stanley <joel@jms.id.au>
Acked-by: Andrew Jeffery <andrew@aj.id.au>
Acked-by: Alexander Filippov <a.filippov@yadro.com>
Link: https://lore.kernel.org/r/20210526051220.136432-1-joel@jms.id.au


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