iommu/sva: include mmu_notifier.h header

A call to mmu_notifier_arch_invalidate_secondary_tlbs() was introduced in
commit e37d5a2d60a3 ("iommu/sva: invalidate stale IOTLB entries for kernel
address space") but without explicitly adding its corresponding header
file <linux/mmu_notifier.h>. This was evidenced while trying to enable
compile testing support for IOMMU_SVA:

config IOMMU_SVA
select IOMMU_MM_DATA
- bool
+ bool "Shared Virtual Addressing" if COMPILE_TEST

The thing is for certain architectures this header file is indirectly
included via <asm/tlbflush.h>. However, for others such as 32-bit arm the
header is missing and it results in a build failure:

$ make ARCH=arm allmodconfig
[...]
drivers/iommu/iommu-sva.c:340:3: error: call to undeclared function 'mmu_notifier_arch_invalidate_secondary_tlbs' [...]
340 | mmu_notifier_arch_invalidate_secondary_tlbs(iommu_mm->mm, start, end);
| ^

Fix this by including the appropriate header file.

Link: https://lkml.kernel.org/r/20260105190747.625082-1-cmllamas@google.com
Fixes: e37d5a2d60a3 ("iommu/sva: invalidate stale IOTLB entries for kernel address space")
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Cc: Baolu Lu <baolu.lu@linux.intel.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Kevin Tian <kevin.tian@intel.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Vasant Hegde <vasant.hegde@amd.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>