octeontx2-af: Fix devlink crash

commit 079cd84d8c8e4e1a274c8544eae302d524cdab15 from
git@git.assembla.com:cavium/WindRiver.linux.git

There were two calls to devlink_unregister() which
caused a crash. Remove one of them

Signed-off-by: Ratheesh Kannoth <rkannoth@marvell.com>
Change-Id: Ic305fae5ccfe0507c7b2316f54356c15a9e176c5
Reviewed-on: https://sj1git1.cavium.com/c/IP/SW/kernel/linux/+/115430


Tested-by: sa_ip-sw-jenkins <sa_ip-sw-jenkins@marvell.com>
Reviewed-by: Sunil Kovvuri Goutham <sgoutham@marvell.com>
Signed-off-by: Ruiqiang Hao <Ruiqiang.Hao@windriver.com>