MIPS: ingenic: Enable JZ4780_NEMC manually

The CONFIG_JZ4780_NEMC was previously a default on MIPS but now it has
to be enabled manually.

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Paul Cercueil <paul@crapouillou.net>
Acked-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>