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 memblock_dbg log in "free_reserved_area".
After adding log:
[    0.294837] memblock_free: [0x00000083600000-0x00000083603000] free_initrd_mem+0x20/0x28
[    0.294848] Freeing initrd memory: 12K.
[    0.695246] memblock_free: [0x00000081600000-0x00000081a00000] free_initmem+0x70/0xc8
[    0.696688] Freeing unused kernel memory: 4096K.

Change-Id: I5ebbb9c1ced481e0ce2acd839e85526aa8dadf75
Signed-off-by: Faiyaz Mohammed <faiyazm@codeaurora.org>