mmc: mmc_test: Uninitialized return value

commit 16652a936e96f5dae53c3fbd38a570497baadaa8 upstream.

We never set "ret" to RESULT_OK.

Fixes: 9f9c4180 ("mmc: mmc_test: add test for non-blocking transfers")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>