manifest: MCUboot and Zephyr changes required for three images

Update sdk-mcuboot and sdk-zephyr revisions to bring in
changes required for support of three images.

Signed-off-by: Dominik Ermel <dominik.ermel@nordicsemi.no>

west.yml

@@ -59,7 +59,7 @@ manifest:
     # https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/zephyr/guides/modules.html
     - name: zephyr
       repo-path: sdk-zephyr
-      revision: 02956222c991e2c036810a5e39fd60e72aa75866
+      revision: pull/1276/head
       import:
         # In addition to the zephyr repository itself, NCS also
         # imports the contents of zephyr/west.yml at the above
@@ -126,7 +126,7 @@ manifest:
           compare-by-default: false
     - name: mcuboot
       repo-path: sdk-mcuboot
-      revision: 54319b44950463936e75b4cf898ba5222083a497
+      revision: pull/270/head
       path: bootloader/mcuboot
     - name: qcbor
       url: https://github.com/laurencelundblade/QCBOR.git