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/include/asm-generic/global_data.h b/include/asm-generic/global_data.h
index c6d63b3..f8fc87f 100644
--- a/include/asm-generic/global_data.h
+++ b/include/asm-generic/global_data.h
@@ -307,7 +307,7 @@
 #if CONFIG_IS_ENABLED(CMD_BDINFO_EXTRA)
 	unsigned long malloc_start;
 #endif
-#if CONFIG_VAL(SYS_MALLOC_F_LEN)
+#if CONFIG_IS_ENABLED(SYS_MALLOC_F)
 	/**
 	 * @malloc_base: base address of early malloc()
 	 */