nsproxy: remove INIT_NSPROXY()

Remove INIT_NSPROXY(), use C99 initializer.
Remove INIT_IPC_NS(), INIT_NET_NS() while I'm at it.

Note: headers trim will be done later, now it's quite pointless because
results will be invalidated by merge window.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>