serial: 8250_early: add xscale earlycon support

After commit 3a50365d ("serial: 8250: Add OF support for Xscale
variant"), 8250_of can support the xscale variant. Now, let's add
the earlycon support for xscale too.

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Link: https://lore.kernel.org/r/20240711160720.3488-3-jszhang@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>