irqchip/gic-v3-its: Fix potential VPE leak on error

In the Linux kernel, the following vulnerability has been resolved: irqchip/gic-v3-its: Fix potential VPE leak on error In its_vpe_irq_domain_alloc, when its_vpe_init() returns an error, there is an off-by-one in the number of VPEs to be freed. Fix it by simply passing the number of VPEs allocated, which is the index of the loop iterating over the VPEs. [maz: fixed commit message]