mm: add kconfig option to control the memory manger strategy choice.

since will will porvide more the one  strategy in future.

Change-Id: I73b900c6571f9b71b8239dd72006bdd0a68ee64d

mm/Kconfig

@@ -3,6 +3,23 @@
 # see the file kconfig-language.txt in the NuttX tools repository.
 #
 
+choice
+	prompt "Build heap manager"
+	default MM_DEFAULT_MANAGER
+
+config MM_DEFAULT_MANAGER
+	bool "Default heap manager"
+	---help---
+		NuttX original memory manager strategy.
+
+config MM_CUSTOMIZE_MANAGER
+	bool "Customized heap manager"
+	---help---
+		Customized memory manger policy. The build will fail
+		if the MM heap module not defined by customer.
+
+endchoice
+
 config MM_KERNEL_HEAP
 	bool "Support a protected, kernel heap"
 	default y

mm/mm_heap/Make.defs

@@ -20,6 +20,8 @@
 
 # Core heap allocator logic
 
+ifeq ($(CONFIG_MM_DEFAULT_MANAGER),y)
+
 CSRCS += mm_initialize.c mm_sem.c mm_addfreechunk.c mm_size2ndx.c
 CSRCS += mm_malloc_usable_size.c mm_shrinkchunk.c
 CSRCS += mm_brkaddr.c mm_calloc.c mm_extend.c mm_free.c mm_mallinfo.c
@@ -38,3 +40,5 @@ endif
 
 DEPPATH += --dep-path mm_heap
 VPATH += :mm_heap
+
+endif # CONFIG_MM_DEFAULT_MANAGER