ppp: Move ioctl definitions from if_ppp.h to new ppp-ioctl.h

This moves the definitions of the ioctls, constants and structures
relating to the ppp_generic interface to userspace out from if_ppp.h
to a new file, ppp-ioctl.h.  The new file has my copyright since I
designed and implemented the ppp_generic interface in the late 1990s.
None of the contents of this file comes from the original if_ppp.h
published by Carnegie Mellon University.

Of the remainder of if_ppp.h, only the PPP_MTU definition was being
used, and this replaces the uses of it with PPP_MRU (which is identical).
Therefore, this replaces the entire file with the single line

#include <linux/ppp-ioctl.h>

which clearly doesn't contain any CMU code.  Thus I have removed the
CMU copyright notice with its problematic advertising clause, and in
fact since it's only one trivial line I have not added any other
copyright notice.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ppp/pptp.c b/drivers/net/ppp/pptp.c
index 234cd9d..885dbdd 100644
--- a/drivers/net/ppp/pptp.c
+++ b/drivers/net/ppp/pptp.c
@@ -23,7 +23,7 @@
 #include <linux/ppp_channel.h>
 #include <linux/ppp_defs.h>
 #include <linux/if_pppox.h>
-#include <linux/if_ppp.h>
+#include <linux/ppp-ioctl.h>
 #include <linux/notifier.h>
 #include <linux/file.h>
 #include <linux/in.h>
@@ -481,7 +481,7 @@
 
 	po->chan.mtu = dst_mtu(&rt->dst);
 	if (!po->chan.mtu)
-		po->chan.mtu = PPP_MTU;
+		po->chan.mtu = PPP_MRU;
 	ip_rt_put(rt);
 	po->chan.mtu -= PPTP_HEADER_OVERHEAD;