armv8r64-extras/xen: Upgrade Xen to 4.17

To achieve this upgrade, the main changes are as follows:
* Switch to use the main Xen Project repository
* Add .bb for xen 4.17 and change to use stable-4.17 branch
* Bump the version to RELEASE-4.17.0
* Do the same for xen-tools 4.17
* Remove downstream patches for shmem and evtchn since their support
  was included in 4.17
* Add Xen support for Armv8-R AArch64 with MPU as downstream patches
* Update Xen's config
* Update device tree, mainly including:
   * Add 'xen,static-heap' settings
   * Update 'xen,static-mem' settings
   * Add 'xen,peer-dom-id' settings
   * Update the shared memory nodes
   * Update event channel nodes:
      * The 'evtchn' nodes are now inside the DomUs
      * Add configs for evtchn in xen_dom0less_config.bbclass
      * Remove obsolete evtchn configs, templates and python code
* Update the Linux driver patches for shmem and evtchn

Issue-Id: SCM-5230
Signed-off-by: Robbie Cao <robbie.cao@arm.com>
Change-Id: I5bd2f7d52817214f36b70fda242dbcf9788a9093