Move initf_malloc() to a common place

To allow this function to be used from SPL, move it to the malloc()
code.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/common/board_f.c b/common/board_f.c
index 90f3b88..322e070 100644
--- a/common/board_f.c
+++ b/common/board_f.c
@@ -23,6 +23,7 @@
 #include <i2c.h>
 #include <initcall.h>
 #include <logbuff.h>
+#include <malloc.h>
 #include <mapmem.h>
 
 /* TODO: Can we move these into arch/ headers? */
@@ -721,17 +722,6 @@
 	return 0;
 }
 
-static int initf_malloc(void)
-{
-#ifdef CONFIG_SYS_MALLOC_F_LEN
-	assert(gd->malloc_base);	/* Set up by crt0.S */
-	gd->malloc_limit = gd->malloc_base + CONFIG_SYS_MALLOC_F_LEN;
-	gd->malloc_ptr = 0;
-#endif
-
-	return 0;
-}
-
 static int initf_dm(void)
 {
 #if defined(CONFIG_DM) && defined(CONFIG_SYS_MALLOC_F_LEN)