Enable the dmi driver for riscv which would allow access the
SMBIOS info through some userspace file(/sys/firmware/dmi/*).

The change was based on that of arm64 and has been verified
by dmidecode tool.
Signed-off-by: Haibo Xu <haibo1.xu@intel.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Link: https://lore.kernel.org/r/20240613065507.287577-1-haibo1.xu@intel.comSigned-off-by: Palmer Dabbelt <palmer@rivosinc.com>