iommu/exynos: Rename update_pte()

The name "update_pte" is a little too generic, and can end up clashing
with architecture pagetable code leaked out of common mm headers. Rename
it to something more appropriately namespaced.

Reported-by: kernel test robot <lkp@intel.com>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>

Link: https://lore.kernel.org/r/829bb5dc18e734870b75db673ddce86e7e37fc73.1594727968.git.robin.murphy@arm.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>