iommu/arm-smmu: Allow inherting stream mapping from bootloader

The Qualcomm bootloaders leaves the IOMMU with stream mapping for
the display hardware to be able to read the framebuffer memory in DDR,
to continuously display a boot splash or to implement EFI framebuffer.

This patch implements support for implementations to pin stream mappings
and adds the code to the Qualcomm implementation for reading out the
stream mapping from the bootloader, with the result of maintaining the
display hardware's access to DDR until the context bank is enabled.

Heavily based on downstream implementation by Patrick Daly
<pdaly@codeaurora.org>.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20191226221709.3844244-4-bjorn.andersson@linaro.org


Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>