MAINTAINERS: Add myself as Ingenic SoCs maintainer

Add myself as the maintainer of the arch code, devicetree files and
drivers related to the JZ47xx family of SoCs from Ingenic.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
[paul.burton@mips.com: Keep list sorted; move after JZ4780 NAND.]
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@vger.kernel.org