hw: aspeed: Ensure AST1030 respects uart-default

hw: aspeed: Ensure AST1030 respects uart-default

The AST1030 machine initialization was not respecting the Aspeed SoC
property "uart-default", which specifies which UART should be connected to
the first serial device, it was just always connecting UART5. This doesn't
change any behavior, because the default value for "uart-default" is UART5,
but it makes it possible to override this in new machine definitions using
the AST1030.

Signed-off-by: Peter Delevoryas <pdel@fb.com>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20220516062328.298336-4-pdel@fb.com>
Signed-off-by: Cédric Le Goater <clg@kaod.org>