net: ethernet: ti: icssg_prueth: fix rx_mgm_chn cleanup on SR1

Currently when I bring down the ICSSG Ethernet interface on a SR1 EVM
and bring it up again, I see following error at the console:-

[   46.991399] icssg-prueth pruss1_eth: PSI-L request err -22
[   46.996920] icssg-prueth pruss1_eth eth1: Failed to request
        rx dma ch: -22
[   47.003879] icssg-prueth pruss1_eth: failed to init rx mgmt
        channel: -22

This patch fixes the issue by doing cleanup of rx_mgm_chn for SR1.

Fixes: 405dbacc ("net: ethernet: ti: icssg_prueth: Support SR2.0")
Signed-off-by: Murali Karicheri <m-karicheri2@ti.com>
Acked-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>