[RPi5] net: cadence: macb: Enable software IRQ coalescing by default

[Daniel J Blueman]

The macb ethernet driver (Raspberry Pi 5) delivers interrupts only to
the first core, quickly saturating it at higher packet rates.

Introducing software interrupt coalescing dramatically alleviates this
limitation; the oneliner fix is upstream in
d57f7b45945ac0517ff8ea50655f00db6e8d637c.

Please backport this fix to the Ubuntu Raspi 6.8 and 6.11 kernels to
bring this benefit to more Raspberry Pis; it applies cleanly on these
branches.

Many thanks,
  Daniel
-- 
Daniel J Blueman