riscv: kprobes: allow writing to x0

commit 8cb22bec upstream.

Instructions can write to x0, so we should simulate these instructions
normally.

Currently, the kernel hangs if an instruction who writes to x0 is
simulated.

Fixes: c22b0bcb ("riscv: Add kprobes supported")
Cc: stable@vger.kernel.org
Signed-off-by: Nam Cao <namcaov@gmail.com>
Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>
Acked-by: Guo Ren <guoren@kernel.org>
Link: https://lore.kernel.org/r/20230829182500.61875-1-namcaov@gmail.com


Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>