board/qemu/aarch64-virt/linux.config: enable ARM_SMMU_V3

board/qemu/aarch64-virt/linux.config: enable ARM_SMMU_V3

>From [1]:
Support for implementations of the ARM System MMU architecture
version 3 providing translation support to a PCIe root complex.

ARM SMMU is supported since Qemu v3.0.0 [2].

ARM_SMMU_V3 can be enabled with: -M virt,iommu=smmuv3

dmesg:
arm-smmu-v3 9050000.smmuv3: ias 44-bit, oas 44-bit (features 0x00000305)
arm-smmu-v3 9050000.smmuv3: allocated 262144 entries for cmdq
arm-smmu-v3 9050000.smmuv3: allocated 131072 entries for evtq

[1] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/drivers/iommu/Kconfig?h=v5.4.42#n390
[2] https://git.qemu.org/?p=qemu.git;a=commitdiff;h=527773eeef9f2225370f9c17c35074b2ed0ced92

Signed-off-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>