Update to YP dunfell 3.1.5

Changes include:
- Backport gstreamer 1.16.2 vs 1.16.3 workaround for rcar3
  (originally for SPEC-3706 in master, now updated per SPEC-3803).
- Add 1.16.% wildcard version of meta-rcar-gen3-adas Kingfisher
  support layer gstreamer1.0-plugins-bad bbappend.  The issue is the
  same as with the main meta-rcar-gen3 BSP layer bbappends mentioned
  above, but this particular bbappend has been disabled in the newer
  BSP in master/koi, so they did not need a fix.
- Add override of PREFERRED_VERSION_libdrm for rcar3 to quiet
  warnings about 2.4.100 not being available, which are caused by
  dunfell 3.1.5 bringing an update to 2.4.101.
- Pin Raspberry Pi kernel version to 4.19.  meta-raspberrypi
  upstream has switched their default kernel to 5.4 on their
  dunfell branch, but that significant of a change is not desirable
  in a AGL point release.
- Remove now upstreamed systemd patch.

Bug-AGL: SPEC-3793, SPEC-3803

Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Change-Id: Ia678b8f56f35026a62a9f6ab40f9727b10756ad6
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl/+/26042
Tested-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>