ARM: dts: sh73a0: Add missing interrupt-affinity to PMU node

The PMU node references two interrupts, but lacks the interrupt-affinity
property, which is required in that case:

    hw perfevents: no interrupt-affinity property for /pmu, guessing.

Add the missing property to fix this.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>