Revert "v4l2object: Use mmap64 to match libv4l2 signature"

This reverts commit b61bba48488c0a627d90f04cc9917d8c4f3f0d9b.
diff --git a/sys/v4l2/gstv4l2object.c b/sys/v4l2/gstv4l2object.c
index c2400d1..81abb5d 100644
--- a/sys/v4l2/gstv4l2object.c
+++ b/sys/v4l2/gstv4l2object.c
@@ -22,8 +22,6 @@
 #include <config.h>
 #endif
 
-#define _GNU_SOURCE             /* Enable mmap64() */
-
 #include <sys/stat.h>
 #include <fcntl.h>
 #include <errno.h>
@@ -515,11 +513,7 @@
     v4l2object->dup = dup;
     v4l2object->ioctl = ioctl;
     v4l2object->read = read;
-#ifdef HAVE_MMAP64
-    v4l2object->mmap = mmap64;
-#else
     v4l2object->mmap = mmap;
-#endif
     v4l2object->munmap = munmap;
   }