tests: maxim_ds3231_api: use fixture

This test depends on additional hardware being connected to the board,
add a fixture and cleanup whitelist.

Fixes zephyrproject-rtos#25177

Signed-off-by: Anas Nashif <anas.nashif@intel.com>

tests/drivers/counter/maxim_ds3231_api/testcase.yaml

@@ -1,8 +1,10 @@
 tests:
   drivers.counter.maxim_ds3231:
     tags: drivers
-    depends_on: counter
+    depends_on: counter i2c
     min_ram: 16
     timeout: 400
     filter: dt_compat_enabled("maxim,ds3231")
-    platform_whitelist: efr32mg_sltb004a frdm_k64f nrf51dk_nrf51422 nrf52840dk_nrf52840 nucleo_l476rg particle_xenon
+    harness: ztest
+    harness_config:
+      fixture: maxim_ds3231