net: drop NET dependency from HAVE_BPF_JIT

There is no point having the NET dependency on the select target, as it
forces all users to depend on NET to tell they support BPF_JIT.  Move
the config option to the bottom of the file - this could be a nice place
also for future "selectable" config symbols.

Fix up all users to drop the dependency on NET now that it is not
required to supress warnings for non-NET builds.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: David Miller <davem@davemloft.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>