MIPS: Loongson: update cpu-feature-overrides.h

Loongson doesn't support MIPSR2, therefore, MIPSR2 vectored interrupts
(cpu_has_vint) and MIPSR2 external interrupt controller mode
(cpu_has_veic) are 0.

Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
Cc: Linux-MIPS <linux-mips@linux-mips.org>
Patchwork: http://patchwork.linux-mips.org/patch/1112/


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