iommu/arm-smmu-v3: Introduce strtab init helper

Introduce a helper to check the sid range and to init the l2 strtab
entries(bypass). This will be useful when we have to initialize the
l2 strtab with bypass for RMR SIDs.

Tested-by: Hanjun Guo <guohanjun@huawei.com>
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Acked-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/20220615101044.1972-7-shameerali.kolothum.thodi@huawei.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>