boards: hifive_unmatched: add support for S7 and U74 targets

Add `hifive_unmatched//s7` (earlier selected by default, using
`hifive_unmatched`) and `hifive_unmatched//u74` targets.

Define work-area for other 4 cores in openocd.cfg

Update twister platform white/black lists, to support new targets

Signed-off-by: Jakub Wasilewski <jwasilewski@internships.antmicro.com>
Signed-off-by: Filip Kokosinski <fkokosinski@antmicro.com>

tests/subsys/fs/ext2/boards/hifive_unmatched_fu740_u74.overlay

@@ -0,0 +1,21 @@
+/*
+ * Copyright (c) 2023 Antmicro
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+&spi2 {
+	status = "okay";
+
+	sdhc0: sdhc@0 {
+		compatible = "zephyr,sdhc-spi-slot";
+		reg = <0>;
+		status = "okay";
+		mmc {
+			compatible = "zephyr,sdmmc-disk";
+			disk-name = "SD";
+			status = "okay";
+		};
+		spi-max-frequency = <20000000>;
+	};
+};

tests/subsys/fs/ext2/testcase.yaml

@@ -5,7 +5,8 @@ tests:
     platform_allow:
       - native_sim
       - native_sim/native/64
-      - hifive_unmatched
+      - hifive_unmatched/fu740/s7
+      - hifive_unmatched/fu740/u74
       - bl5340_dvk/nrf5340/cpuapp
     extra_args:
       - EXTRA_DTC_OVERLAY_FILE="ramdisk_small.overlay"
@@ -22,7 +23,8 @@ tests:
     simulation_exclude:
       - renode
     platform_allow:
-      - hifive_unmatched
+      - hifive_unmatched/fu740/s7
+      - hifive_unmatched/fu740/u74
       - bl5340_dvk/nrf5340/cpuapp
     extra_args: CONF_FILE=prj_sdcard.conf