tests: boards: esp32: cache_coex: add esp32s2

Add esp32s2_saola to supported platforms

Signed-off-by: Lucas Tamborrino <lucas.tamborrino@espressif.com>
diff --git a/tests/boards/espressif_esp32/cache_coex/testcase.yaml b/tests/boards/espressif_esp32/cache_coex/testcase.yaml
index 3b89433..bcb037b 100644
--- a/tests/boards/espressif_esp32/cache_coex/testcase.yaml
+++ b/tests/boards/espressif_esp32/cache_coex/testcase.yaml
@@ -1,6 +1,6 @@
 tests:
   boards.esp32.cache_coex:
-    platform_allow: esp32
+    platform_allow: esp32 esp32s2_saola
     tags:
       - spiram
       - spiflash