MIPS: Pistachio: Support 8250-based early printk

Pistachio SoCs are capable of early printk with generic 8250 support,
so let's select the options to enable it.

Signed-off-by: Ezequiel Garcia <ezequiel.garcia@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Andrew Bresticker <abrestic@chromium.org>
Cc: James Hartley <james.hartley@imgtec.com>
Patchwork: https://patchwork.linux-mips.org/patch/9913/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>