slirp: Clean up ifs_init

Remove duplicate ifs_init macros, reimplement the logic as static inline
in mbuf.h.

CC: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
CC: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>

slirp/if.c

@@ -8,8 +8,6 @@
 #include <slirp.h>
 #include "qemu-timer.h"
 
-#define ifs_init(ifm) ((ifm)->ifs_next = (ifm)->ifs_prev = (ifm))
-
 static void
 ifs_insque(struct mbuf *ifm, struct mbuf *ifmhead)
 {

slirp/if.h

@@ -20,6 +20,4 @@
 /* 2 for alignment, 14 for ethernet, 40 for TCP/IP */
 #define IF_MAXLINKHDR (2 + 14 + 40)
 
-#define ifs_init(ifm) ((ifm)->ifs_next = (ifm)->ifs_prev = (ifm))
-
 #endif

slirp/mbuf.h

@@ -124,4 +124,9 @@ void m_adj(struct mbuf *, int);
 int m_copy(struct mbuf *, struct mbuf *, int, int);
 struct mbuf * dtom(Slirp *, void *);
 
+static inline void ifs_init(struct mbuf *ifm)
+{
+    ifm->ifs_next = ifm->ifs_prev = ifm;
+}
+
 #endif