ACPI-based Loongson boards need configurable rather than fixed clock
frequency for serial ports.
Signed-off-by: NJianmin Lv <lvjianmin@loongson.cn>
Signed-off-by: NHuacai Chen <chenhuacai@loongson.cn>
Link: https://lore.kernel.org/r/20210715061637.134436-1-chenhuacai@loongson.cnSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>