Cleanup: Separate the netlink method to cgre_receive_netlink_msg().

Cleanup: Separate the netlink method to cgre_receive_netlink_msg().

Hi,

Changelog of v6:
================
 * No change.

Changelog of v5:
================
 * No change.

Changelog of v4:
================
 * Remove unused parameter "cn_hdr" from cgre_receive_netlink_msg().

Changelog of v3:
================
 * No change.

Changelog of v2:
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 * New patch.

Description:
============
This patch separates the netlink method for the readability, because
the later patch [PATCH 6/9] adds "unix domain socket" handling method
around the netlink method.

Thanks
Ken'ichi Ohmichi

Signed-off-by: Ken'ichi Ohmichi <oomichi@mxs.nes.nec.co.jp>
Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>