manifest: Bring in imgtool support for PureEdDSA signatures

Brings changes to imgtool that are required to have support
for PureEdDSA.

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

west.yml

@@ -132,7 +132,7 @@ manifest:
           compare-by-default: true
     - name: mcuboot
       repo-path: sdk-mcuboot
-      revision: 22adc04fc4b35a6ee477675c8a33e038a98258de
+      revision: pull/342/head
       path: bootloader/mcuboot
     - name: qcbor
       url: https://github.com/laurencelundblade/QCBOR