Request to backport "irqchip/gic-v3-its: Fix misuse of GENMASK macro"

Hi Greg, Sasha,

Could you please help to backport the upstream commit 20faba848752901de23a4d45a1174d64d2069dde ("irqchip/gic-v3-its: Fix misuse of GENMASK macro") to the stable linux-4.19 tree since it's definitely a fix for 4.19. Note that it's not needed for other stable trees.

I've tried and it can be applied to 4.19.106 cleanly.

Thanks, Zenghui