riscv: uaccess: fix __put_user_nocheck for unaligned accesses

The type of the value to write should be determined by the size of the
destination, not by the value itself, which may be a constant. This
aligns the behavior with x86_64, where __typeof__(*(__gu_ptr)) is used
to infer the correct type.

This fixes an issue in put_cmsg, which was only writing 4 out of 8
bytes to the cmsg_len field, causing the glibc tst-socket-timestamp test
to fail.

Fixes: ca1a66c ("riscv: uaccess: do not do misaligned accesses in get/put_user()")
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20250724220853.1969954-1-aurelien@aurel32.net
Signed-off-by: Paul Walmsley <pjw@kernel.org>

Author: aurel32

arch/riscv/include/asm/uaccess.h

@@ -311,7 +311,7 @@ do {								\
 do {								\
 	if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) &&	\
 	    !IS_ALIGNED((uintptr_t)__gu_ptr, sizeof(*__gu_ptr))) {	\
-		__inttype(x) ___val = (__inttype(x))x;			\
+		__typeof__(*(__gu_ptr)) ___val = (x);		\
 		if (__asm_copy_to_user_sum_enabled(__gu_ptr, &(___val), sizeof(*__gu_ptr))) \
 			goto label;				\
 		break;						\