iommu/pages: Remove iommu_alloc_page/pages()

A few small changes to the remaining drivers using these will allow
them to be removed:

- Exynos wants to allocate fixed 16K/8K allocations
- Rockchip already has a define SPAGE_SIZE which is used by the
  dma_map immediately following, using SPAGE_ORDER which is a lg2size
- tegra has size constants already for its two allocations

Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20-v4-c8663abbb606+3f7-iommu_pages_jgg@nvidia.com


Signed-off-by: Joerg Roedel <jroedel@suse.de>