LU-1337 llite: kernel 3.1 kills inode->i_alloc_sem

LU-1337 llite: kernel 3.1 kills inode->i_alloc_sem

Kernel 3.1 kills inode->i_alloc_sem, use i_dio_count and
inode_dio_wait/inode_dio_done instead.
(kernel commit bd5fe6c5eb9c548d7f07fe8f89a150bb6705e8e3).

Add HAVE_INODE_DIO_WAIT to differentiate it.

Signed-off-by: Liu Xuezhao <xuezhao.liu@emc.com>
Change-Id: Ife36e07a85c76153985a4a86ee1973262c4c0e27
Reviewed-on: http://review.whamcloud.com/3582
Tested-by: Hudson
Reviewed-by: Jinshan Xiong <jinshan.xiong@whamcloud.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>