btrfs: merge alloc_device helpers

The device allocation is split to two functions, but one just calls the
other and they're very far in the file. Merge them together.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
David Sterba 2021-07-26 14:15:21 +02:00
commit fe4f46d40c