iommu/arm-smmu: Add support to handle Qcom's wait-for-safe logic

Qcom's implementation of arm,mmu-500 adds a WAIT-FOR-SAFE logic
to address under-performance issues in real-time clients, such as
Display, and Camera.
On receiving an invalidation requests, the SMMU forwards SAFE request
to these clients and waits for SAFE ack signal from real-time clients.
The SAFE signal from such clients is used to qualify the start of
invalidation.
This logic is controlled by chicken bits, one for each - MDP (display),
IFE0, and IFE1 (camera), that can be accessed only from secure software
on sdm845.

This configuration, however, degrades the performance of non-real time
clients, such as USB, and UFS etc. This happens because, with wait-for-safe
logic enabled the hardware tries to throttle non-real time clients while
waiting for SAFE ack signals from real-time clients.

On MTP sdm845 devices, with wait-for-safe logic enabled at the boot time
by the bootloaders we see degraded performance of USB and UFS when kernel
enables the smmu stage-1 translations for these clients.
Turn off this wait-for-safe logic from the kernel gets us back the perf
of USB and UFS devices until we re-visit this when we start seeing perf
issues on display/camera on upstream supported SDM845 platforms.

Now, different bootloaders with their access control policies allow this
register access differently through secure monitor calls -
1) With one we can issue io-read/write secure monitor call (qcom-scm)
   to update the register, while,
2) With other, such as one on MTP sdm845 we should use the specific
   qcom-scm command to send request to do the complete register
   configuration.
Adding a separate device tree flag for arm-smmu to identify which
firmware configuration of the two mentioned above we use.
Not adding code change to allow type-(1) bootloaders to toggle the
safe using io-read/write qcom-scm call.

This change is inspired by the downstream change from Patrick Daly
to address performance issues with display and camera by handling
this wait-for-safe within separte io-pagetable ops to do TLB
maintenance. So a big thanks to him for the change.

Without this change the UFS reads are pretty slow:
$ time dd if=/dev/sda of=/dev/zero bs=1048576 count=10 conv=sync
10+0 records in
10+0 records out
10485760 bytes (10.0MB) copied, 22.394903 seconds, 457.2KB/s
real    0m 22.39s
user    0m 0.00s
sys     0m 0.01s

With this change they are back to rock!
$ time dd if=/dev/sda of=/dev/zero bs=1048576 count=300 conv=sync
300+0 records in
300+0 records out
314572800 bytes (300.0MB) copied, 1.030541 seconds, 291.1MB/s
real    0m 1.03s
user    0m 0.00s
sys     0m 0.54s

Signed-off-by: Vivek Gautam <vivek.gautam@codeaurora.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Ondrej Kubik <ondrej.kubik@canonical.com>