bcache: Move spinlock into struct time_stats

Minor cleanup.

Signed-off-by: Kent Overstreet <kmo@daterainc.com>

diff --cc drivers/md/bcache/bcache.h
Simple merge

diff --cc drivers/md/bcache/bset.c
Simple merge

diff --cc drivers/md/bcache/btree.c
Simple merge

diff --cc drivers/md/bcache/super.c
Simple merge

diff --cc drivers/md/bcache/util.c
Simple merge

diff --cc drivers/md/bcache/util.h
Simple merge