DDN-3473 build: support kernel 3.10.0-693.el7

DDN-3473 build: support kernel 3.10.0-693.el7

This patch fixes the following build failures to support
kernel 3.10.0-693.el7 for Lustre client:

- error: implicit declaration of function 'idr_destroy'
- error: implicit declaration of function 'gfpflags_allow_blocking'
- error: implicit declaration of function ‘cdev_device_add’
- error: passing argument 1 of 'init_wait_var_entry' from
  incompatible pointer type

Test-Parameters: trivial
Signed-off-by: Jian Yu <yujian@whamcloud.com>
Change-Id: I4b5c5264fb102d3a825c92e7b1e92cf0c52540e5
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/49197
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>