iommu/amd: Prevent NULL pointer dereference

mainline inclusion
from mainline-v5.10-rc1
commit 23357b61
category: bugfix
bugzilla: 43219
CVE: NA

------------------------------------------------

Dereferencing irq_data before checking it for NULL is suboptimal.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Joerg Roedel <jroedel@suse.de>

Conflicts:
	drivers/iommu/amd/iommu.c
Signed-off-by: Chen Huang <chenhuang5@huawei.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>