[nrf fromtree] boards: nordic: nrf54l20pdk: Add dmic to supported peripherals

Add dmic to the list of supported peripherals on nRF54L20pdk.

Signed-off-by: Sebastian Głąb <[email protected]>
(cherry picked from commit 0015571)

Author: nordic-segl

boards/nordic/nrf54l20pdk/nrf54l20pdk_nrf54l20_cpuapp.yaml

@@ -15,6 +15,7 @@ flash: 449
 supported:
   - adc
   - counter
+  - dmic
   - gpio
   - i2c
   - pwm