armv8r64-extras/zephyr: Add recipe for SDK 0.15.1 & inc for kernel 3.2.0

The main changes are as below:

* Use the same branch as the defaults setting, for meta-zephyr

* Set PREFERRED_VERSION_zephyr-kernel to 3.2.0

* Add recipe for the Zephyr SDK v0.15.1

  Zephyr 3.2.0 requires Zephyr SDK version >= 0.15.0, so add a recipe
  to meta-armv8r64-extras for 0.15.1 which requires the upstream
  0.14.2 recipe.

* Add .inc file for Zephyr 3.2.0

  Use the generate-versions.py script in meta-zephyr-core to generate a
  .inc file for meta-zephyr containing the Yocto modules and SRCREVs for
  Zephyr 3.2.0

  The version-specific include file is currently included using a local
  include relative to meta-zephyr-core, so as a workaround re-require
  the new .inc file in the fvp-baser-aemv8r64 machine bbappend.

Issue-Id: SCM-4874
Signed-off-by: Peter Hoyes <Peter.Hoyes@arm.com>
Signed-off-by: Robbie Cao <robbie.cao@arm.com>
Change-Id: I3e9e71c1cdbb902329be86060650e86f0b63688b