[nrf noup] samples: smp_svr: nrf54h mcuboot + b0 board variant support

Added nrf54h20dk/nrf54h20/cpuapp/iron/mcuboot/b0 in the supported
boards list for the subsys/mgmt/mcumgr/smp_svr sample in the
serial variant.

Signed-off-by: Artur Hadasz <[email protected]>

Author: ahasztag

samples/subsys/mgmt/mcumgr/smp_svr/sample.yaml

@@ -92,6 +92,7 @@ tests:
       - rd_rw612_bga
       - nrf52840dk/nrf52840
       - nrf54h20dk/nrf54h20/cpuapp/iron
+      - nrf54h20dk/nrf54h20/cpuapp/iron/mcuboot/b0
       - pinnacle_100_dvk
       - mg100
     integration_platforms: