fix pppac(4) without pipex

[YASUOKA Masahiko]

Hi,

The diff followings fixes panics when using pppac(4) with "pipex no".

Index: sys/net/if_pppx.c
===================================================================
RCS file: /cvs/src/sys/net/if_pppx.c,v
retrieving revision 1.83
diff -u -p -r1.83 if_pppx.c
--- sys/net/if_pppx.c   10 Apr 2020 07:36:52 -0000      1.83
+++ sys/net/if_pppx.c   12 Apr 2020 06:12:35 -0000
@@ -344,7 +344,7 @@ pppxwrite(dev_t dev, struct uio *uio, in
        if (m == NULL)
                return (ENOBUFS);
        mlen = MHLEN;
-       if (uio->uio_resid >= MINCLSIZE) {
+       if (uio->uio_resid > MHLEN) {
                MCLGET(m, M_DONTWAIT);
                if (!(m->m_flags & M_EXT)) {
                        m_free(m);
@@ -1368,7 +1368,7 @@ pppacwrite(dev_t dev, struct uio *uio, i
        if (m == NULL)
                return (ENOMEM);
 
-       if (uio->uio_resid > MINCLSIZE) {
+       if (uio->uio_resid > MHLEN) {
                m_clget(m, M_WAITOK, uio->uio_resid);
                if (!ISSET(m->m_flags, M_EXT)) {
                        m_free(m);