tests: memc: Update yaml to support da1469x_dk_pro

Testing with external PSRAM memory requires that an extra overlay file
be defined.

Signed-off-by: Ioannis Karachalios <[email protected]>

Author: ioannis-karachalios

tests/drivers/memc/ram/testcase.yaml

@@ -8,3 +8,5 @@ tests:
     depends_on: memc
     integration_platforms:
       - sam4s_xplained
+    extra_args:
+      - platform:da1469x_dk_pro:EXTRA_DTC_OVERLAY_FILE="da1469x_dk_pro_psram.overlay"