iommufd: Allow a hwpt to be aborted after allocation

iommufd: Allow a hwpt to be aborted after allocation

During creation the hwpt must have the ioas->mutex held until the object
is finalized. This means we need to be able to call
iommufd_object_abort_and_destroy() while holding the mutex.

Since iommufd_hw_pagetable_destroy() also needs the mutex this is
problematic.

Fix it by creating a special abort op for the object that can assume the
caller is holding the lock, as required by the contract.

The next patch will add another iommufd_object_abort_and_destroy() for a
hwpt.

Fixes: e8d57210035b ("iommufd: Add kAPI toward external drivers for physical devices")
Link: https://lore.kernel.org/r/10-v8-6659224517ea+532-iommufd_alloc_jgg@nvidia.com
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>