octeontx2-pf: Fix transmit scheduler resource leak

[ Upstream commit bccb798e ]

Inorder to support shaping and scheduling, Upon class creation
Netdev driver allocates trasmit schedulers.

The previous patch which added support for Round robin scheduling has
a bug due to which driver is not freeing transmit schedulers post
class deletion.

This patch fixes the same.

Fixes: 47a9656f ("octeontx2-pf: htb offload support for Round Robin scheduling")
Signed-off-by: Hariprasad Kelam <hkelam@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>