defconfig: Enable cnss_genl driver compilation

cnss_genl driver creates a netlink family and multicast groups
to facilitate communication between WLAN driver and userspace.
Define flag CONFIG_CNSS_GENL to enable compilation
of the cnss_genl driver inorder to use the same. 

Change-Id: I5cc257acb8c5b16f839e6a3c3d8d5116fbf772f3
Signed-off-by: Sandeep Singh <sandsing@codeaurora.org>
CRs-Fixed: 2346674