iommu: arm-smmu: Add atos self test

Add atos self test to perform atos for different sids. To enable,
set CONFIG_ARM_SMMU_SELFTEST and arm_smmu.selftest=1 and set the
sids and masks in arm_smmu.selftestsids in the below format
smmu_name,no_of_sids,sid:mask.

for eg: arm_smmu.selftestsids=kgsl,0x1,0x7:0x400,apps,0x2,
	0x1:0x0,0x51f:0x0

Change-Id: I74134ed712e06a17b1570256e2ee3820df2f4457
Signed-off-by: Charan Teja Reddy <charante@codeaurora.org>
Signed-off-by: Prakash Gupta <guptap@codeaurora.org>
Signed-off-by: Vijayanand Jitta <vjitta@codeaurora.org>