firmware: turris-mox-rwtm: Fix checking return value of wait_for_completion_timeout()

The wait_for_completion_timeout() function returns 0 if timed out, and a
positive value if completed. Fix the usage of this function.

Fixes: 389711b3 ("firmware: Add Turris Mox rWTM firmware driver")
Fixes: 2eab59cf ("firmware: turris-mox-rwtm: fail probing when firmware does not support hwrng")
Signed-off-by: Marek Behún <kabel@kernel.org>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

drivers/firmware/turris-mox-rwtm.c

@@ -202,9 +202,8 @@ static int mox_get_board_info(struct mox_rwtm *rwtm)
 	if (ret < 0)
 		return ret;
 
-	ret = wait_for_completion_timeout(&rwtm->cmd_done, HZ / 2);
-	if (ret < 0)
-		return ret;
+	if (!wait_for_completion_timeout(&rwtm->cmd_done, HZ / 2))
+		return -ETIMEDOUT;
 
 	ret = mox_get_status(MBOX_CMD_BOARD_INFO, reply->retval);
 	if (ret == -ENODATA) {
@@ -238,9 +237,8 @@ static int mox_get_board_info(struct mox_rwtm *rwtm)
 	if (ret < 0)
 		return ret;
 
-	ret = wait_for_completion_timeout(&rwtm->cmd_done, HZ / 2);
-	if (ret < 0)
-		return ret;
+	if (!wait_for_completion_timeout(&rwtm->cmd_done, HZ / 2))
+		return -ETIMEDOUT;
 
 	ret = mox_get_status(MBOX_CMD_ECDSA_PUB_KEY, reply->retval);
 	if (ret == -ENODATA) {
@@ -277,9 +275,8 @@ static int check_get_random_support(struct mox_rwtm *rwtm)
 	if (ret < 0)
 		return ret;
 
-	ret = wait_for_completion_timeout(&rwtm->cmd_done, HZ / 2);
-	if (ret < 0)
-		return ret;
+	if (!wait_for_completion_timeout(&rwtm->cmd_done, HZ / 2))
+		return -ETIMEDOUT;
 
 	return mox_get_status(MBOX_CMD_GET_RANDOM, rwtm->reply.retval);
 }