block/brd: add error handling support for add_disk()

mainline inclusion
from mainline-v5.16-rc1
commit e1528830
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I81XCK

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e1528830bd4ebf435d91c154e309e6e028336210



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We never checked for errors on add_disk() as this function
returned void. Now that this is fixed, use the shiny new
error handling.

Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Link: https://lore.kernel.org/r/20211015235219.2191207-2-mcgrof@kernel.org


Signed-off-by: Jens Axboe <axboe@kernel.dk>
conflict:
  drivers/block/brd.c
Signed-off-by: Zhong Jinghua <zhongjinghua@huawei.com>
Signed-off-by: Li Nan <linan122@huawei.com>