mmc: Fix mmc_switch excessive timeout

Fix branching to avoid premature falling back on a long timeout instead
of continuation of the initialization attempt.

Clear of the comment to avoid the ambiguity.

Signed-off-by: Kirill Kapranov <kirill.kapranov@compulab.co.il>
Cc: Pantelis Antoniou <panto@antoniou-consulting.com>
Cc: Ye Li <ye.li@nxp.com>
Reviewed-by: Marek Behún <marek.behun@nic.cz>
Tested-by: Marek Behún <marek.behun@nic.cz>
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>