Merge branch 'net-more-heap-allocation-and-split-of-rtnl_newlink'

Jakub Kicinski says:

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net: more heap allocation and split of rtnl_newlink()

Small refactoring of rtnl_newlink() to fix a stack usage warning
and make the function shorter.
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Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Paolo Abeni <[email protected]>