bcache: fix error info in register_bcache()

In register_bcache(), there are several cases we didn't set
correct error info (return value and/or error message):
- if kzalloc() fails, it needs to return ENOMEM and print
"cannot allocate memory";
- if register_cache() fails, it's better to propagate its
return value rather than using default EINVAL.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Coly Li <colyli@suse.de>
Link: https://lore.kernel.org/r/20211020143812.6403-4-colyli@suse.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>