octeontx2-pf: Fix memory leak during interface down

During 'ifconfig <netdev> down' one RSS memory was not getting freed.
This patch fixes the same.

Fixes: 81a43620 ("octeontx2-pf: Add RSS multi group support")
Signed-off-by: Suman Ghosh <sumang@marvell.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>