net: account alternate interface name memory

[ Upstream commit 5d26cff5 ]

George reports that altnames can eat up kernel memory.
We should charge that memory appropriately.

Reported-by: George Shuklin <george.shuklin@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>