tests: drivers: SPI: Replace OVERLAY_CONFIG with EXTRA_CONF_FILE

Replace OVERLAY_CONFIG with EXTRA_CONF_FILE as the former
is deprecated.

Signed-off-by: Emil Gydesen <[email protected]>

Author: Thalley

tests/drivers/spi/spi_loopback/testcase.yaml

@@ -279,7 +279,7 @@ tests:
       - s32z2xxdc2/s32z270/rtu1
   drivers.spi.max32_spi_rtio.loopback:
     extra_args:
-      - OVERLAY_CONFIG="overlay-max32-spi-rtio.conf"
+      - EXTRA_CONF_FILE="overlay-max32-spi-rtio.conf"
     filter: CONFIG_SOC_FAMILY_MAX32
     platform_allow:
       - apard32690/max32690/m4