mmc: moxart: Fix null pointer dereference on pointer host

mmc: moxart: Fix null pointer dereference on pointer host

There are several error return paths that dereference the null pointer
host because the pointer has not yet been set to a valid value.
Fix this by adding a new out_mmc label and exiting via this label
to avoid the host clean up and hence the null pointer dereference.

Addresses-Coverity: ("Explicit null dereference")
Fixes: 8105c2abbf36 ("mmc: moxart: Fix reference count leaks in moxart_probe")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Link: https://lore.kernel.org/r/20211013100052.125461-1-colin.king@canonical.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>