The commit "btrfs: scrub: inline helper scrub_setup_wr_ctx" inlined a
helper but wrongly sets up the target device. Incidentally there's a
local variable with the same name as a parameter in the previous
function, so this got caught during runtime as crash in test btrfs/027.
Reported-by: NChris Mason <clm@fb.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>