xen/arm: p2m: Re-implement relinquish_p2m_mapping using p2m_{get,set}_entry

xen/arm: p2m: Re-implement relinquish_p2m_mapping using p2m_{get,set}_entry

The function relinquish_p2m_mapping can be re-implemented using
p2m_{get,set}_entry by iterating over the range mapped and using the
mapping order given by the callee.

Given that the preemption was chosen arbitrarily, it is now done on every
512 iterations. Meaning that Xen may check more often if the function is
preempted when there are no mappings.

Finally drop the operation RELINQUISH in apply_* as nobody is using it
anymore. Note that the functions could have been dropped in one go at
the end, however I find easier to drop the operations one by one
avoiding a big deletion in the patch that remove the last operation.

Signed-off-by: Julien Grall <julien.grall@arm.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Tested-by: Tamas K Lengyel <tamas@tklengyel.com>