riscv: Fixup difference with defconfig

Let's follow the origin patch's spirit:

The only difference between rv32_defconfig and defconfig is that
rv32_defconfig has  CONFIG_ARCH_RV32I=y.

This is helpful to compare rv64-compat-rv32 v.s. rv32-linux.

Fixes: 1b937e8f ("RISC-V: Add separate defconfig for 32bit systems")
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20220405071314.3225832-9-guoren@kernel.org


Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>