Merge branch 'genetlink-remove-linux-genetlink-h'

Jakub Kicinski says:

====================
genetlink: remove linux/genetlink.h

There are two genetlink headers net/genetlink.h and linux/genetlink.h
This is similar to netlink.h, but for netlink.h both contain good
amount of code. For genetlink.h the linux/ version is leftover
from before uAPI headers were split out, it has 10 lines of code.
Move those 10 lines into other appropriate headers and delete
linux/genetlink.h.

I occasionally open the wrong header in the editor when coding,
I guess I'm not the only one.

v2: https://lore.kernel.org/all/20240325173716.2390605-1-kuba@kernel.org/
v1: https://lore.kernel.org/all/20240309183458.3014713-1-kuba@kernel.org
====================

Link: https://lore.kernel.org/r/20240329175710.291749-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>