ublk: fix maple tree lockdep warning and unpin under spinlock#761

blktests-ci[bot] wants to merge 1 commit intolinus-master_baselinux-blktests/linux-block:linus-master_basefrom

series/1084082=>linus-masterlinux-blktests/linux-block:series/1084082=>linus-masterCopy head branch name to clipboard