mm: page_alloc: Add debug log in free_reserved_area for static memory

For INITRD and initmem memory is reserved through "memblock_reserve"
during boot up but it is free via "free_reserved_area" instead
of "memblock_free".
For example:
[    0.294848] Freeing initrd memory: 12K.
[    0.696688] Freeing unused kernel memory: 4096K.

To get the start and end address of the above freed memory and to account
proper memblock added pr_debug log in "free_reserved_area".
After adding log:
[    0.294837] 0x00000083600000-0x00000083603000 free_initrd_mem+0x20/0x28
[    0.294848] Freeing initrd memory: 12K.
[    0.695246] 0x00000081600000-0x00000081a00000 free_initmem+0x70/0xc8
[    0.696688] Freeing unused kernel memory: 4096K.

Signed-off-by: Faiyaz Mohammed <faiyazm@codeaurora.org>

mm/page_alloc.c

@@ -8097,6 +8097,8 @@ EXPORT_SYMBOL(adjust_managed_page_count);
 
 unsigned long free_reserved_area(void *start, void *end, int poison, const char *s)
 {
+	const phys_addr_t pstart = __pa(start);
+	const phys_addr_t pend = __pa(end);
 	void *pos;
 	unsigned long pages = 0;
 
@@ -8125,9 +8127,12 @@ unsigned long free_reserved_area(void *start, void *end, int poison, const char
 		free_reserved_page(page);
 	}
 
-	if (pages && s)
+	if (pages && s) {
 		pr_info("Freeing %s memory: %ldK\n",
 			s, pages << (PAGE_SHIFT - 10));
+		pr_debug("[%pa-%pa] %pS\n", &pstart, &pend,
+			(void *)__RET_IP_);
+	}
 
 	return pages;
 }