tests: drivers: flash: Add support "common" for Renesas ek_ra4l1

Add support test app "flash/common" for Renesas RA ek_ra4l1

Signed-off-by: Khoa Nguyen <[email protected]>

Author: khoa-nguyen-18

tests/drivers/flash/common/boards/ek_ra4l1.conf

@@ -0,0 +1,4 @@
+# Copyright (c) 2025 Renesas Electronics Corporation
+# SPDX-License-Identifier: Apache-2.0
+
+CONFIG_TEST_DRIVER_FLASH_SIZE=8192