wireguard: selftests: set CONFIG_NONPORTABLE on riscv32

wireguard: selftests: set CONFIG_NONPORTABLE on riscv32

When the CONFIG_PORTABLE/CONFIG_NONPORTABLE switches were added, various
configs were updated, but the wireguard config was forgotten about. This
leads to unbootable test kernels, causing CI fails. Add
CONFIG_NONPORTABLE=y to the wireguard test suite configuration for
riscv32.

Fixes: 2a2c64dedb14 ("RISC-V: Add CONFIG_{NON,}PORTABLE")
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20220809145757.83673-1-Jason@zx2c4.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>