iommu/arm: Add BBM Level 2 smmu feature

iommu/arm: Add BBM Level 2 smmu feature

For supporting BBM Level 2 for userspace mappings, we want to ensure
that the smmu also supports its own version of BBM Level 2. Luckily, the
smmu spec (IHI 0070G 3.21.1.3) is stricter than the aarch64 spec (DDI
0487K.a D8.16.2), so already guarantees that no aborts are raised when
BBM level 2 is claimed.

Add the feature and testing for it under arm_smmu_sva_supported().

Signed-off-by: Mikołaj Lenczewski <miko.lenczewski@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Link: https://lore.kernel.org/r/20250625113435.26849-4-miko.lenczewski@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>