Merge branch 'net-deduplicate-netdev-name-allocation'

Jakub Kicinski says:

====================
net: deduplicate netdev name allocation

After recent fixes we have even more duplicated code in netdev name
allocation helpers. There are two complications in this code.
First, __dev_alloc_name() clobbers its output arg even if allocation
fails, forcing callers to do extra copies. Second as our experience in
commit 55a5ec9b7710 ("Revert "net: core: dev_get_valid_name is now the same as dev_alloc_name_ns"") and
commit 029b6d140550 ("Revert "net: core: maybe return -EEXIST in __dev_alloc_name"")
taught us, user space is very sensitive to the exact error codes.

Align the callers of __dev_alloc_name(), and remove some of its
complexity.

v1: https://lore.kernel.org/all/20231020011856.3244410-1-kuba@kernel.org/
====================

Link: https://lore.kernel.org/r/20231023152346.3639749-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>