MIPS: generic/yamon-dt: Use serial* rather than uart* aliases

MIPS: generic/yamon-dt: Use serial* rather than uart* aliases

Name aliases in the SEAD-3 device tree serial0 & serial1, rather than
uart0 & uart1. This allows the core serial code to make use of the
aliases to ensure that the UARTs are consistently numbered as expected
rather than having the numbering depend upon probe order.

When translating YAMON-provided serial configuration to a device tree
stdout-path property adjust accordingly, such that we continue to
reference a valid alias.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16183/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>