iommu/arm-smmu-v3: Stop pre-zeroing batch commands in arm_smmu_atc_inv_master()

iommu/arm-smmu-v3: Stop pre-zeroing batch commands in arm_smmu_atc_inv_master()

Pre-zeroing the batched commands structure is inefficient, as individual
commands are zeroed later in arm_smmu_cmdq_build_cmd(). Therefore, only
the member 'num' needs to be initialized to 0.

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Reviewed-by: John Garry <john.garry@huawei.com>
Link: https://lore.kernel.org/r/20210817113411.1962-1-thunder.leizhen@huawei.com
Signed-off-by: Will Deacon <will@kernel.org>