MIPS: ingenic: Initial JZ4780 support

Support the Ingenic JZ4780 SoC using the existing code under
arch/mips/jz4740 now that it has been generalised sufficiently.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: Ian Campbell <ijc+devicetree@hellion.org.uk>
Cc: Kumar Gala <galak@codeaurora.org>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Pawel Moll <pawel.moll@arm.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: devicetree@vger.kernel.org
Cc: linux-mips@linux-mips.org
Cc: Joshua Kinard <kumba@gentoo.org>
Cc: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Cc: Deng-Cheng Zhu <dengcheng.zhu@imgtec.com>
Cc: linux-kernel@vger.kernel.org
Cc: Markos Chandras <markos.chandras@imgtec.com>
Cc: Andreas Herrmann <andreas.herrmann@caviumnetworks.com>
Patchwork: https://patchwork.linux-mips.org/patch/10164/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>