spl: Use SYS_MALLOC_F instead of SYS_MALLOC_F_LEN

Use the new SPL/TPL/VPL_SYS_MALLOC_F symbols to determine whether the
malloc pool exists.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Sean Anderson <sean.anderson@seco.com>
diff --git a/common/board_r.c b/common/board_r.c
index e309633..5278690 100644
--- a/common/board_r.c
+++ b/common/board_r.c
@@ -191,7 +191,7 @@
 {
 	ulong start;
 
-#if CONFIG_VAL(SYS_MALLOC_F_LEN)
+#if CONFIG_IS_ENABLED(SYS_MALLOC_F)
 	debug("Pre-reloc malloc() used %#lx bytes (%ld KB)\n", gd->malloc_ptr,
 	      gd->malloc_ptr / 1024);
 #endif