LU-1576 llite: correct page usage count

LU-1576 llite: correct page usage count

If kernel has add_to_page_cache_lru(), the ll_pagevec_add() is defined
as an empty function, while page_cache_get(page) only makes sense if
ll_pagevec_add() is defined.

This patch moves page_cache_get into ll_pagevec_add() macro
definition.

Signed-off-by: Bobi Jam <bobijam@whamcloud.com>
Change-Id: Iad98aacff43beec3e7a64fd1a778f549250aa5b8
Reviewed-on: http://review.whamcloud.com/3255
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Lai Siyao <laisiyao@whamcloud.com>
Reviewed-by: Fan Yong <yong.fan@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>