configure: improve misleading libnl missing error message

This fixes a misleading error message saying the libnl package
needs to be installed, when it's really the libnl-devel package
needing to be installed.

configure.ac

@@ -2215,7 +2215,7 @@ LIBNL_LIBS=""
 if test "$with_macvtap" = "yes"; then
     PKG_CHECK_MODULES([LIBNL], [libnl-1 >= $LIBNL_REQUIRED], [
     ], [
-        AC_MSG_ERROR([libnl >= $LIBNL_REQUIRED is required for macvtap support])
+        AC_MSG_ERROR([libnl-devel >= $LIBNL_REQUIRED is required for macvtap support])
     ])
 fi