ANDROID: mm: allow hooks into free_pages_prepare()

Allow drivers to register mm_page_free hooks when free pages.
This helps to get page info when free pages exit.

Bug: 348514795
Change-Id: I1f2e1844aa24836367da65e8bfe11f79e22713d4
Signed-off-by: Qinglin Li <qinglin.li@amlogic.com>

mm/page_alloc.c

@@ -64,6 +64,7 @@
 #include "page_reporting.h"
 
 EXPORT_TRACEPOINT_SYMBOL_GPL(mm_page_alloc);
+EXPORT_TRACEPOINT_SYMBOL_GPL(mm_page_free);
 
 /* Free Page Internal flags: for internal, non-pcp variants of free_pages(). */
 typedef int __bitwise fpi_t;