ARM: dts: r8a73a4: Add missing CMT1 interrupts

The R-Mobile APE6 Compare Match Timer 1 generates 8 interrupts, one for
each channel, but currently only 1 is described.
Fix this by adding the missing interrupts.

Fixes: f7b65230 ("ARM: shmobile: r8a73a4: Add CMT1 node")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20200408090926.25201-1-geert+renesas@glider.be