ptpbuf / 7D: sync "uncacheable" macro with mem.h

These shouldn't be in two places, but I'm not fixing it now.

src/ptpbuf.h

@@ -1,7 +1,19 @@
 #ifndef _ptpbuf_h_
 #define _ptpbuf_h_
 
-#define UNCACHEABLE(x)   ((void*)(((uint32_t)(x)) | 0x40000000))
+/* Cacheable/uncacheable RAM pointers */
+// SJE FIXME: why does ptpbuf.h define these as well as mem.h?
+// The definitions must be kept in sync for 7D builds, which
+// link against ptpbuf.o, or gcc complains about redefinition
+// of the define (sensibly).
+#ifdef CONFIG_VXWORKS
+#define UNCACHEABLE(x) ((void*)(((uint32_t)(x)) |  0x10000000))
+#define CACHEABLE(x)   ((void*)(((uint32_t)(x)) & ~0x10000000))
+#else
+#define UNCACHEABLE(x) ((void*)(((uint32_t)(x)) | (((uint32_t)(x)) < 0x40000000 ?  0x40000000 : 0)))
+#define CACHEABLE(x)   ((void*)(((uint32_t)(x)) & ~0x40000000))
+#endif
+
 #define PTPBUF_BUFS      16
 #define PTPBUF_BUFSIZE   256
 #define PTPBUF_MAGIC     0xEAEA3388