[GCC4] fix warnings in include/net/dn_nsp.h

[GCC4] fix warnings in include/net/dn_nsp.h

This patch fixes these warnings with gcc 4 :

In file included from dn_route.c:81:
/usr/src/git/linux-2.4/include/net/dn_nsp.h:75: warning: 'packed' attribute ignored for field of type 'unsigned char'
/usr/src/git/linux-2.4/include/net/dn_nsp.h:97: warning: 'packed' attribute ignored for field of type 'unsigned char'
/usr/src/git/linux-2.4/include/net/dn_nsp.h:106: warning: 'packed' attribute ignored for field of type 'unsigned char'
(...)