erofs: fix erofs_insert_workgroup() lockref usage

erofs: fix erofs_insert_workgroup() lockref usage

[ Upstream commit 1a0ac8bd7a4fa5b2f4ef14c3b1e9d6e5a5faae06 ]

As Linus pointed out [1], lockref_put_return() is fundamentally
designed to be something that can fail.  It behaves as a fastpath-only
thing, and the failure case needs to be handled anyway.

Actually, since the new pcluster was just allocated without being
populated, it won't be accessed by others until it is inserted into
XArray, so lockref helpers are actually unneeded here.

Let's just set the proper reference count on initializing.

[1] https://lore.kernel.org/r/CAHk-=whCga8BeQnJ3ZBh_Hfm9ctba_wpF444LpwRybVNMzO6Dw@mail.gmail.com

Fixes: 7674a42f35ea ("erofs: use struct lockref to replace handcrafted approach")
Reviewed-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20231031060524.1103921-1-hsiangkao@linux.alibaba.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>