CI: Remove uniquely zephyr machines

Remove microbit-v1, qemu-cortex-a53, qemu-cortex-m3, and qemu-cortex-r5
from CI (and the tree in general).  These machines are part of the
meta-zephyr CI now and keeping them here is redundant.  However, keeping
zephyr builds for machines that also have TF-M.

Signed-off-by: Jon Mason <jon.mason@arm.com>

ci/microbit-v1.yml

@@ -1,7 +0,0 @@
-header:
-  version: 11
-  includes:
-    - ci/base.yml
-    - ci/meta-zephyr.yml
-
-machine: microbit-v1

ci/qemu-cortex-a53.yml

@@ -1,9 +0,0 @@
-header:
-  version: 11
-  includes:
-    - ci/base.yml
-    - ci/meta-zephyr.yml
-
-# FIXME - testimage fails all tests currently, but all the tests build
-
-machine: qemu-cortex-a53

ci/qemu-cortex-m3.yml

@@ -1,20 +0,0 @@
-header:
-  version: 11
-  includes:
-    - ci/base.yml
-    - ci/meta-zephyr.yml
-
-repos:
-  meta-zephyr:
-    layers:
-      meta-zephyr-bsp:
-
-local_conf_header:
-  tclibc: |
-    TCLIBC = "newlib"
-  nonbuilding_tests: |
-    ZEPHYRTESTS:remove = "common context pending poll sleep"
-  qemu_opts: |
-    QB_OPT_APPEND = "-icount shift=3,align=off,sleep=on -rtc clock=vm"
-
-machine: qemu-cortex-m3

ci/qemu-cortex-r5.yml

@@ -1,11 +0,0 @@
-header:
-  version: 11
-  includes:
-    - ci/base.yml
-    - ci/meta-zephyr.yml
-
-local_conf_header:
-  nonbuilding_tests: |
-    ZEPHYRTESTS:remove = "common poll sleep queue device"
-
-machine: qemu-cortex-r5