mmc: fix CONFIG_MMC_UNSAFE_RESUME regression

30201e7f ("mmc: skip detection of nonremovable cards on rescan")
allowed skipping detection of nonremovable cards on mmc_rescan().
The intention was to only skip detection of hardwired cards that
cannot be removed, so make sure this is indeed the case by directly
checking for (lack of) MMC_CAP_NONREMOVABLE, instead of using
mmc_card_is_removable(), which is overloaded with
CONFIG_MMC_UNSAFE_RESUME semantics.

The user-visible symptom of the bug this patch fixes is that no
"mmc: card XXXX removed" message appears in dmesg when a card is
removed and CONFIG_MMC_UNSAFE_RESUME=y.

Reported-and-tested-by: Dmitry Shmidt <dimitrysh@google.com>
Reported-and-tested-by: Maxim Levitsky <maximlevitsky@gmail.com>
Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>
Signed-off-by: Chris Ball <cjb@laptop.org>