target/riscv: SMBIOS support for RISC-V virt machine

Generate SMBIOS tables for the RISC-V mach-virt.
Add CONFIG_SMBIOS=y to the RISC-V default config.
Set the default processor family in the type 4 table.

The implementation is based on the corresponding ARM and Loongson code.

With the patch the following firmware tables are provided:

    etc/smbios/smbios-anchor
    etc/smbios/smbios-tables

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Message-ID: <20240123184229.10415-4-heinrich.schuchardt@canonical.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

hw/riscv/Kconfig

@@ -41,6 +41,7 @@ config RISCV_VIRT
     select RISCV_IMSIC
     select SIFIVE_PLIC
     select SIFIVE_TEST
+    select SMBIOS
     select VIRTIO_MMIO
     select FW_CFG_DMA
     select PLATFORM_BUS