configs/hifive_unleashed: Update to use U-Boot v2023.04

With upstream commit ae2d9506a36c ("riscv: sifive: Rename fu540 board to unleashed")
in U-Boot v2021.07 release, the defconfig for SiFive Unleashed board
has been changed to sifive_unleashed_defconfig.

Also newer U-Boot has deprecated the usage of SPL_FIT_GENERATOR
to generate u-boot.itb hence there is no 'u-boot.itb' target in
the U-Boot Makefile anymore. Instead binman is used to assemble
the u-boot.itb image.

We will need to switch to BR2_TARGET_UBOOT_FORMAT_CUSTOM for
installing u-boot.itb.

Switch over to use the latest U-Boot v2023.04 release.

Signed-off-by: Bin Meng <bmeng@tinylab.org>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

configs/hifive_unleashed_defconfig

@@ -42,12 +42,13 @@ BR2_TARGET_OPENSBI_CUSTOM_VERSION_VALUE="1.2"
 BR2_TARGET_OPENSBI_PLAT="generic"
 BR2_TARGET_UBOOT=y
 BR2_TARGET_UBOOT_CUSTOM_VERSION=y
-BR2_TARGET_UBOOT_CUSTOM_VERSION_VALUE="2021.01"
+BR2_TARGET_UBOOT_CUSTOM_VERSION_VALUE="2023.04"
 BR2_TARGET_UBOOT_BUILD_SYSTEM_KCONFIG=y
-BR2_TARGET_UBOOT_BOARD_DEFCONFIG="sifive_fu540"
+BR2_TARGET_UBOOT_BOARD_DEFCONFIG="sifive_unleashed"
 BR2_TARGET_UBOOT_NEEDS_DTC=y
 BR2_TARGET_UBOOT_NEEDS_OPENSBI=y
-BR2_TARGET_UBOOT_FORMAT_ITB=y
+BR2_TARGET_UBOOT_FORMAT_CUSTOM=y
+BR2_TARGET_UBOOT_FORMAT_CUSTOM_NAME="u-boot.itb"
 BR2_TARGET_UBOOT_SPL=y
 
 # Host tools