mmc: block: Fix error path in mmc_blk_probe()

mmc: block: Fix error path in mmc_blk_probe()

Returning zero to indicate success, when we actually have failed to probe
is wrong. As a matter of fact, it leads to that mmc_blk_remove() gets
called at a card removal and then triggers "NULL pointer dereference"
splats. This is because mmc_blk_remove() relies on data structures and
pointers to be setup from mmc_blk_probe(), of course.

There have been no errors reported about this, which is most likely because
mmc_blk_probe() never fails like this. Nevertheless, let's fix the code by
propagating the error codes correctly and prevent us from leaking memory by
calling also destroy_workqueue() in the error path.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20210303122049.151986-4-ulf.hansson@linaro.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>