net: Remove task_struct::bpf_net_context init on fork.

There is no clone() invocation within a bpf_net_ctx_…() block. Therefore
the task_struct::bpf_net_context has always to be NULL and an explicit
initialisation is not required.

Remove the NULL assignment in the clone() path.

Suggested-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/r/20240628103020.1766241-2-bigeasy@linutronix.de


Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>