RISC-V: Fix the rv32i kernel build
These patches for building 32-bit RISC-V kernel.
- Fix the compile errors and warnings on RV32I.
- Fix some incompatible problem on RV32I.
- Add format.h for compatible of print format.
The fixed width integer types format for Elf_Addr will move to
generic header by another patch. For now, there are some warning
about unexpected argument of type on RV32I.
Change in v1:
- Fix some error in v1
- Remove implementation of fixed width integer types format for Elf_Addr.
