include/uapi/linux/ppp-ioctl.h: pull in ppp_defs.h

include/uapi/linux/ppp-ioctl.h: pull in ppp_defs.h

This header uses enum NPmode but doesn't include ppp_defs.h.  If you try
to use this header w/out including the defs header first, it leads to a
build failure.  So add the explicit include to fix it.

Don't know of any packages directly impacted, but noticed while building
some ppp code by hand.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>