netdevsim: remove incorrect __net_initdata annotations

The __net_initdata section cannot currently be used for structures that
get cleaned up in an exitcall using unregister_pernet_operations:

WARNING: vmlinux.o(.text+0x868c34): Section mismatch in reference from the function nsim_devlink_exit() to the (unknown reference) .init.data:(unknown)
The function nsim_devlink_exit() references
the (unknown reference) __initdata (unknown).
This is often because nsim_devlink_exit lacks a __initdata
annotation or the annotation of (unknown) is wrong.
WARNING: vmlinux.o(.text+0x868c64): Section mismatch in reference from the function nsim_devlink_init() to the (unknown reference) .init.data:(unknown)
WARNING: vmlinux.o(.text+0x8692bc): Section mismatch in reference from the function nsim_fib_exit() to the (unknown reference) .init.data:(unknown)
WARNING: vmlinux.o(.text+0x869300): Section mismatch in reference from the function nsim_fib_init() to the (unknown reference) .init.data:(unknown)

As that warning tells us, discarding the structure after a module is
loaded would lead to a undefined behavior when that module is removed.

It might be possible to change that annotation so it has no effect for
loadable modules, but I have not figured out exactly how to do that, and
we want this to be fixed in -rc1.

This just removes the annotations, just like we do for all other such
modules.

Fixes: 37923ed6

 ("netdevsim: Add simple FIB resource controller via devlink")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>