MAINTAINERS: add Loongson1 architecture entry

This patch adds Loongson1 architecture entry.

Signed-off-by: Kelvin Cheung <keguang.zhang@gmail.com>
Cc: Michael Turquette <mturquette@baylibre.com>
Cc: Stephen Boyd <sboyd@codeaurora.org>
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Alexandre Courbot <gnurou@gmail.com>
Cc: Boris Brezillon <boris.brezillon@free-electrons.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Brian Norris <computersforpeace@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: linux-clk@vger.kernel.org
Cc: linux-pm@vger.kernel.org
Cc: dmaengine@vger.kernel.org
Cc: linux-gpio@vger.kernel.org
Cc: linux-mtd@lists.infradead.org
Patchwork: https://patchwork.linux-mips.org/patch/13034/


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