bdi: test bdi_init failure

There were two places where return value from bdi_init was not tested.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --cc fs/char_dev.c
Simple merge

diff --cc include/linux/backing-dev.h
Simple merge

diff --cc mm/swap.c
Simple merge