[nrf noup] dts: nrf21540-fem default tx-en-settle-time-us=26

The default value of the `tx-en-settle-time-us` property is set
to 26 to avoid spurious emission issue.

Signed-off-by: Andrzej Kuros <[email protected]>

Author: ankuns

dts/bindings/net/wireless/nordic,nrf21540-fem.yaml

@@ -95,7 +95,7 @@ properties:
         This must be present to support SPI control of the FEM.
   tx-en-settle-time-us:
     type: int
-    default: 11
+    default: 26
     description: |
         Settling time in microseconds from state PG to TX.