boards: convert SiFive HiFive Unmatched to Zephyr HWMv2

This commit converts the SiFive HiFive Unmatched board (`hifive_unmatched`
target) to the Zephyr Hardware Model v2.

Signed-off-by: Filip Kokosinski <fkokosinski@antmicro.com>

boards/boards_legacy/riscv/hifive_unmatched/hifive_unmatched_defconfig

@@ -1,8 +0,0 @@
-CONFIG_SOC_SERIES_SIFIVE_FREEDOM_U700=y
-CONFIG_SOC_SIFIVE_FREEDOM_U740=y
-CONFIG_BOARD_HIFIVE_UNMATCHED=y
-CONFIG_CONSOLE=y
-CONFIG_SERIAL=y
-CONFIG_UART_SIFIVE_PORT_0=y
-CONFIG_UART_CONSOLE=y
-CONFIG_XIP=n

boards/sifive/hifive_unmatched/Kconfig.defconfig

@@ -3,13 +3,10 @@
 
 if BOARD_HIFIVE_UNMATCHED
 
-config BOARD
-	default "hifive_unmatched"
-
 config SYS_CLOCK_TICKS_PER_SEC
 	default 1000
 
 config SYS_CLOCK_HW_CYCLES_PER_SEC
 	default 1000000
 
-endif
+endif # BOARD_HIFIVE_UNMATCHED

boards/sifive/hifive_unmatched/Kconfig.hifive_unmatched

@@ -2,5 +2,4 @@
 # SPDX-License-Identifier: Apache-2.0
 
 config BOARD_HIFIVE_UNMATCHED
-	bool "HiFive Unmatched target"
-	depends on SOC_SIFIVE_FREEDOM_U740
+	select SOC_SIFIVE_FREEDOM_FU740

boards/sifive/hifive_unmatched/board.yml

@@ -0,0 +1,5 @@
+board:
+  name: hifive_unmatched
+  vendor: sifive
+  socs:
+    - name: fu740

boards/sifive/hifive_unmatched/hifive_unmatched_defconfig

@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: Apache-2.0
+
+CONFIG_CONSOLE=y
+CONFIG_SERIAL=y
+CONFIG_UART_SIFIVE_PORT_0=y
+CONFIG_UART_CONSOLE=y
+CONFIG_XIP=n