irqchip/gic-v3-its: Move pending table allocation to init time

[ Upstream commit 4a0819bb25d12d39c0390636122eefba232596c1 ]

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
[bigeasy: backport commit effe377d415 ("irqchip/gic-v3-its: Move pending
          table allocation to init time")]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>