CVE-2026-63798: irqchip/imgpdc: Fix resource leak, add missing chained handler cleanup on remove

In the Linux kernel, the following vulnerability has been resolved:

irqchip/imgpdc: Fix resource leak, add missing chained handler cleanup on remove

The driver allocates domain generic chips using irqallocdomaingenericchips() during probe and sets up chained handlers using irqsetchainedhandleranddata(). However, on driver removal, the generic chips are not freed and the chained handlers are not removed.

The generic chips remain on the global gclist and may later be accessed by generic interrupt chip suspend, resume, or shutdown callbacks after the driver has been removed, potentially resulting in a use-after-free and kernel crash.

The chained handlers that were installed in probe for peripheral and syswake interrupts are also left dangling, which can lead to spurious interrupts accessing freed memory.

Fix these issues by:

- Setting IRQDOMAINFLAGDESTROYGC flag in domain->flags, so the core code automatically removes generic chips when irqdomainremove() is called

- Clearing all chained handlers with NULL in pdcintcremove()