mmc: skip reclaiming host on mmc_add_card() error

There's little sense in releasing the host on mmc_add_card() error
immediately after reclaiming  it, so reclaim the host  only in case
of success.

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>