replace malloc macros in imports.h with u_memory.h versions

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Kristian H. Kristensen <hoegsberg@google.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3024>

src/mesa/tnl/t_vertex.c

@@ -29,6 +29,7 @@
 #include "main/glheader.h"
 #include "main/context.h"
 #include "main/execmem.h"
+#include "util/u_memory.h"
 #include "swrast/s_chan.h"
 #include "t_context.h"
 #include "t_vertex.h"