irqchip/gic-v5: Fix kmemleak L2 IST table entries false positives

L2 IST table entries are allocated with the kmalloc interface and their
physical addresses are programmed in the GIC (either IST base address
register or L1 IST table entries) but their virtual addresses are not
stored in any kernel data structure because they are not needed at runtime
- the L2 IST table entries are managed through system instructions but
never dereferenced directly by the driver.

This triggers kmemleak false positive reports:

unreferenced object 0xffff00080039a000 (size 4096):
  comm "swapper/0", pid 0, jiffies 4294892296
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace (crc 0):
    kmemleak_alloc+0x34/0x40
    __kmalloc_noprof+0x320/0x464
    gicv5_irs_iste_alloc+0x1a4/0x484
    gicv5_irq_lpi_domain_alloc+0xe4/0x194
    irq_domain_alloc_irqs_parent+0x78/0xd8
    gicv5_irq_ipi_domain_alloc+0x180/0x238
    irq_domain_alloc_irqs_locked+0x238/0x7d4
    __irq_domain_alloc_irqs+0x88/0x114
    gicv5_of_init+0x284/0x37c
    of_irq_init+0x3b8/0xb18
    irqchip_init+0x18/0x40
    init_IRQ+0x104/0x164
    start_kernel+0x1a4/0x3d4
    __primary_switched+0x8c/0x94

Instruct kmemleak to ignore L2 IST table memory allocation virtual
addresses to prevent these false positive reports.

Reported-by: Jinjie Ruan <ruanjinjie@huawei.com>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Jinjie Ruan <ruanjinjie@huawei.com>
Reviewed-by: Zenghui Yu <yuzenghui@huawei.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/all/20250811135001.1333684-1-lpieralisi@kernel.org
Closes: https://lore.kernel.org/lkml/cc611dda-d1e4-4793-9bb2-0eaa47277584@huawei.com/

Author: Lorenzo Pieralisi

drivers/irqchip/irq-gic-v5-irs.c

@@ -5,6 +5,7 @@
 
 #define pr_fmt(fmt)	"GICv5 IRS: " fmt
 
+#include <linux/kmemleak.h>
 #include <linux/log2.h>
 #include <linux/of.h>
 #include <linux/of_address.h>
@@ -117,6 +118,7 @@ static int __init gicv5_irs_init_ist_linear(struct gicv5_irs_chip_data *irs_data
 		kfree(ist);
 		return ret;
 	}
+	kmemleak_ignore(ist);
 
 	return 0;
 }
@@ -232,6 +234,7 @@ int gicv5_irs_iste_alloc(const u32 lpi)
 		kfree(l2ist);
 		return ret;
 	}
+	kmemleak_ignore(l2ist);
 
 	/*
 	 * Make sure we invalidate the cache line pulled before the IRS