MIPS: Loongson: Remove ad-hoc cmdline default

MIPS: Loongson: Remove ad-hoc cmdline default

Loongson builds have an ad-hoc cmdline default of "console=ttyS0,115200
root=/dev/hda1". These settings come from a vendor; I remember builds
from Lemote branch requiring a "console=tty" override in order to get a
working console.

At least on Yeeloong, they're particularly useless: there's no external
serial port, and the IDE drive is now recognised as /dev/sda.

Signed-off-by: Robert Millan <rmh@gnu.org>
To: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/1759/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>