ensure we always have 256bytes net data size, excluding 4 bytes headroom

src/target/firmware/comm/msgb.c

@@ -35,7 +35,7 @@ void *tall_msgb_ctx;
 
 #ifdef NO_TALLOC
 /* This is a poor mans static allocator for msgb objects */
-#define MSGB_DATA_SIZE	256
+#define MSGB_DATA_SIZE	256+4
 #define MSGB_NUM	16
 struct supermsg {
 	uint8_t allocated;

src/target/firmware/include/comm/sercomm_cons.h

@@ -2,7 +2,7 @@
 #define _SERCOMM_CONS_H
 
 /* how large buffers do we allocate? */
-#define SERCOMM_CONS_ALLOC	(256-4)
+#define SERCOMM_CONS_ALLOC	256
 
 int sercomm_puts(const char *s);
 int sercomm_putchar(int c);