mmc: fix a deadlock between system suspend and MMC block IO
Performing MMC block IO with simultaneous STR can lead to a deadlock: the
mmc_pm_notify() function claims the host and then calls bus .remove()
method, which lands in mmc_blk_remove(), which calls mmc_blk_remove_req()
then it goes to -> mmc_cleanup_queue() -> kthread_stop(), which waits for
the mmc-block thread to stop. If the mmc-block thread at that time is
processing block requests, it will also try to claim the host in
mmc_blk_issue_rq() and block there. This patch fixes the problem by
calling .remove() before claiming the host.