samples: modbus: update/fix samples.yaml configs

Update the sample.yaml files for the modbus samples:
- depends_on entries should just be space separated, drop the comma
- add the platform referenced in the documentation to platform_allow
- replace the deprecated dt_compat_enabled_with_alias with
  dt_enabled_alias_with_parent_compat

Signed-off-by: Fabio Baltieri <fabio.baltieri@gmail.com>

samples/subsys/modbus/rtu_client/sample.yaml

@@ -2,5 +2,6 @@ sample:
   name: Modbus RTU Client Sample
 tests:
   sample.modbus.rtu_client:
+    platform_allow: nrf52840dk_nrf52840 frdm_k64f
     tags: uart modbus
-    depends_on: gpio, arduino_serial
+    depends_on: gpio arduino_serial

samples/subsys/modbus/rtu_server/sample.yaml

@@ -2,8 +2,9 @@ sample:
   name: Modbus RTU Server Sample
 tests:
   sample.modbus.rtu_server:
+    platform_allow: nrf52840dk_nrf52840 frdm_k64f
     tags: uart modbus
-    filter: dt_compat_enabled_with_alias("gpio-leds", "led0") and
-            dt_compat_enabled_with_alias("gpio-leds", "led1") and
-            dt_compat_enabled_with_alias("gpio-leds", "led2")
-    depends_on: gpio, arduino_serial
+    filter: dt_enabled_alias_with_parent_compat("led0", "gpio-leds") and
+            dt_enabled_alias_with_parent_compat("led1", "gpio-leds") and
+            dt_enabled_alias_with_parent_compat("led2", "gpio-leds")
+    depends_on: gpio arduino_serial

samples/subsys/modbus/tcp_gateway/sample.yaml

@@ -2,7 +2,8 @@ sample:
   name: Modbus TCP to serial line gateway sample
 tests:
   sample.modbus.tcp_gateway:
+    platform_allow: frdm_k64f
     tags: modbus
-    depends_on: gpio, netif, arduino_serial
+    depends_on: gpio netif arduino_serial
     integration_platforms:
       - frdm_k64f

samples/subsys/modbus/tcp_server/sample.yaml

@@ -2,8 +2,9 @@ sample:
   name: Modbus TCP Server Sample
 tests:
   sample.modbus.tcp_server:
+    platform_allow: frdm_k64f
     tags: modbus
-    filter: dt_compat_enabled_with_alias("gpio-leds", "led0") and
-            dt_compat_enabled_with_alias("gpio-leds", "led1") and
-            dt_compat_enabled_with_alias("gpio-leds", "led2")
-    depends_on: gpio, netif
+    filter: dt_enabled_alias_with_parent_compat("led0", "gpio-leds") and
+            dt_enabled_alias_with_parent_compat("led1", "gpio-leds") and
+            dt_enabled_alias_with_parent_compat("led2", "gpio-leds")
+    depends_on: gpio netif