virtio-blk: drop config_mutex
config_mutex served two purposes: prevent multiple concurrent config
change handlers, and synchronize access to config_enable flag.
Since commit
dbf2576e37da0fcc7aacbfbb9fd5d3de7888a3c1
workqueue: make all workqueues non-reentrant
all workqueues are non-reentrant, and config_enable
is now gone.
Get rid of the unnecessary lock.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>