riscv; fix __user annotation in save_v_state()

The save_v_state() is technically sending a __user pointer through
__put_user() and thus is generating a sparse warning so force the
value to be "void *" to fix:

arch/riscv/kernel/signal.c:94:16: warning: incorrect type in initializer (different address spaces)
arch/riscv/kernel/signal.c:94:16: expected void *__val
arch/riscv/kernel/signal.c:94:16: got void [noderef] __user *[assigned] datap

Fixes: 8ee0b418 ("riscv: signal: Add sigcontext save/restore for vector")
Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Link: https://lore.kernel.org/r/20231123142708.261733-1-ben.dooks@codethink.co.ukSigned-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/kernel/signal.c

@@ -91,7 +91,7 @@ static long save_v_state(struct pt_regs *regs, void __user **sc_vec)
 	err = __copy_to_user(&state->v_state, &current->thread.vstate,
 			     offsetof(struct __riscv_v_ext_state, datap));
 	/* Copy the pointer datap itself. */
-	err |= __put_user(datap, &state->v_state.datap);
+	err |= __put_user((__force void *)datap, &state->v_state.datap);
 	/* Copy the whole vector content to user space datap. */
 	err |= __copy_to_user(datap, current->thread.vstate.datap, riscv_v_vsize);
 	/* Copy magic to the user space after saving  all vector conetext */