samples: matter: Split configurations for Eagle EK tests

We need two separate configurations for nRF52840DK + nrf21540ek
and nRF5340 + nrf21540ek because there are different extra_args
used.

Signed-off-by: Arkadiusz Balys <arkadiusz.balys@nordicsemi.no>

samples/matter/light_bulb/sample.yaml

@@ -25,8 +25,13 @@ tests:
     extra_args: SHIELD=nrf21540ek
     integration_platforms:
       - nrf52840dk_nrf52840
+    platform_allow: nrf52840dk_nrf52840
+  sample.matter.light_bulb.debug.nrf21540ek_fwd:
+    build_only: true
+    extra_args: SHIELD=nrf21540ek_fwd multiprotocol_rpmsg_SHIELD=nrf21540ek
+    integration_platforms:
       - nrf5340dk_nrf5340_cpuapp
-    platform_allow: nrf52840dk_nrf52840 nrf5340dk_nrf5340_cpuapp
+    platform_allow: nrf5340dk_nrf5340_cpuapp
   # Sample to execute load tests
   sample.matter.light_bulb.persistent_subscriptions:
     build_only: true