iommu/pages: De-inline the substantial functions

These are called in a lot of places and are not trivial. Move them to the
core module.

Tidy some of the comments and function arguments, fold
__iommu_alloc_account() into its only caller, change
__iommu_free_account() into __iommu_free_page() to remove some
duplication.

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Mostafa Saleh <smostafa@google.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Tested-by: Alejandro Jimenez <alejandro.j.jimenez@oracle.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/7-v4-c8663abbb606+3f7-iommu_pages_jgg@nvidia.com


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