MIPS: ralink: add MT7621 support

MT7621 is based on a 1004k core. This patch adds support for the SoC. The
timer and IRQ is just boiler plate as GIC has recently been moved to
generic places in the kernel and just works.

Signed-off-by: John Crispin <blogic@openwrt.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/11990/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/mach-ralink/irq.h

@@ -0,0 +1,9 @@
+#ifndef __ASM_MACH_RALINK_IRQ_H
+#define __ASM_MACH_RALINK_IRQ_H
+
+#define GIC_NUM_INTRS	64
+#define NR_IRQS 256
+
+#include_next <irq.h>
+
+#endif