net: ethernet: ti: am65-cpsw: Fix the incorrect resolution when merging v5.15.157

There is only one simple commit 83115775 ("net: ethernet: ti:
am65-cpsw-nuss: cleanup DMA Channels before using them") which touched
drivers/net/ethernet/ti/am65-cpsw-nuss.c between v5.15.156 and
v5.15.157. But when merging of v5.15.157, some unrelated changes
slipped in, while the changes in 83115775 were lost. Drop all the
unrelated changes and restore the commit 83115775 back.

Signed-off-by: Kevin Hao <kexin.hao@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>