iommu/exynos: Abstract non-common registers on different variants

At the moment the driver supports SysMMU v1..v5 versions. SysMMU v5 has
different register layout than SysMMU v1..v3. Instead of checking the
version each time before reading/writing the registers, let's create
corresponding register structure for each SysMMU version and set the
needed structure on init, checking the SysMMU version one single time.
This way is faster and more elegant.

No behavior changes from the user's point of view, it's only a
refactoring patch.

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/r/20220714165550.8884-5-semen.protsenko@linaro.org
Signed-off-by: Joerg Roedel <jroedel@suse.de>