malloc_simple: Add debug() information

It's useful to get a a trace of memory allocations in early init. Add a
debug() call to provide that. It can be enabled by adding '#define DEBUG'
to the top of the file.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/common/malloc_simple.c b/common/malloc_simple.c
index c745863..dd1119f 100644
--- a/common/malloc_simple.c
+++ b/common/malloc_simple.c
@@ -19,10 +19,13 @@
 	void *ptr;
 
 	new_ptr = gd->malloc_ptr + bytes;
+	debug("%s: size=%zx, ptr=%lx, limit=%lx\n", __func__, bytes, new_ptr,
+	      gd->malloc_limit);
 	if (new_ptr > gd->malloc_limit)
 		return NULL;
 	ptr = map_sysmem(gd->malloc_base + gd->malloc_ptr, bytes);
 	gd->malloc_ptr = ALIGN(new_ptr, sizeof(new_ptr));
+
 	return ptr;
 }
 
@@ -37,6 +40,7 @@
 		return NULL;
 	ptr = map_sysmem(addr, bytes);
 	gd->malloc_ptr = ALIGN(new_ptr, sizeof(new_ptr));
+
 	return ptr;
 }