netns: remove BUG_ONs from net_generic()

netns: remove BUG_ONs from net_generic()

This inline has ~500 callsites.

On 04/14/2015 08:37 PM, David Miller wrote:
> That BUG_ON() was added 7 years ago, and I don't remember it ever
> triggering or helping us diagnose something, so just remove it and
> keep the function inlined.

On x86 allyesconfig build:

    text     data      bss       dec     hex filename
82447071 22255384 20627456 125329911 77861f7 vmlinux4
82441375 22255384 20627456 125324215 7784bb7 vmlinux5prime

Signed-off-by: Denys Vlasenko <[email protected]>
CC: Eric W. Biederman <[email protected]>
CC: David S. Miller <[email protected]>
CC: Jan Engelhardt <[email protected]>
CC: Jiri Pirko <[email protected]>
CC: [email protected]
CC: [email protected]
Signed-off-by: David S. Miller <[email protected]>