aw_nmi: add support for a83t's r_intc

[kevans]

Summary

We currently support the a83t's r_intc in a somewhat hack-ish way; our .dts describes it as nmi_intc, and uses a subset of the actual register space to make it line up with a20/a31 nmi offsets.

This will break with the4.14 update describing r_intc using the full register space, so update aw_nmi to use the correct register offsets with the right compat data in a way that doesn't break our current dts with nmi_intc or upstream with r_intc described.

[manu]

This is also needed for A31/A31s as the binding changed also in 4.14, I'll make the necessary changes for this SoC after this is commited.
Thanks

[manu]

sys/arm/allwinner/aw_nmi.c

114 ↗

(On Diff #35332)

You can also modify this compatible to be 'allwinner,sun6i-a31-r-intc', A83T fallback on this as they are compatible.

[kevans]

Ping @emaste, can I push this (+ adding a31 r-intc compat w/ a83t_r_nmi_cfg) through tonight?

[emaste]

After @manu's review, you have my approval.