FROMLIST: iommu/iova: Support limiting IOVA alignment

When the IOVA framework applies IOVA alignment it aligns all
IOVAs to the smallest PAGE_SIZE order which is greater than or
equal to the requested IOVA size.

We support use cases that requires large buffers (> 64 MB in
size) to be allocated and mapped in their stage 1 page tables.
However, with this alignment scheme we find ourselves running
out of IOVA space for 32 bit devices, so we are proposing this
config, along the similar vein as CONFIG_CMA_ALIGNMENT for CMA
allocations.

Add CONFIG_IOMMU_LIMIT_IOVA_ALIGNMENT to limit the alignment of
IOVAs to some desired PAGE_SIZE order, specified by
CONFIG_IOMMU_IOVA_ALIGNMENT. This helps reduce the impact of
fragmentation caused by the current IOVA alignment scheme, and
gives better IOVA space utilization.

Bug: 148141615
Link: https://lore.kernel.org/lkml/alpine.DEB.2.10.2002141223510.27047@lmark-linux.qualcomm.com/


Change-Id: I511ac685d5855e1b9feb5025e025ebbebee7f40d
Signed-off-by: Liam Mark <lmark@codeaurora.org>