memstick: core: avoid -Wnonnull warning

gcc-7 produces a harmless false-postive warning about a possible NULL pointer access:

drivers/memstick/core/memstick.c: In function 'h_memstick_read_dev_id':
drivers/memstick/core/memstick.c:309:3: error: argument 2 null where non-null expected [-Werror=nonnull]
memcpy(mrq->data, buf, mrq->data_len);

This can't happen because the caller sets the command to 'MS_TPC_READ_REG', which causes the data direction to be 'READ' and the NULL pointer not accessed.

As a simple workaround for the warning, we can pass a pointer to the data that we actually want to read into. This is not needed here, but also harmless, and lets the compiler know that the access is ok.

---
 drivers/memstick/core/memstick.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index a0547dbf9806..76382c858c35 100644
@@ -330,7 +330,7 @@ static int h_memstick_read_dev_id(struct memstick_dev *card,
 	struct ms_id_register id_reg;
 
 	if (!(*mrq)) {
-		memstick_init_req(&card->current_mrq, MS_TPC_READ_REG, NULL,
+		memstick_init_req(&card->current_mrq, MS_TPC_READ_REG, &id_reg,
 				  sizeof(struct ms_id_register));
 		*mrq = &card->current_mrq;
 		return 0;

2.9.0