net: mvpp2: Don't re-use loop iterator

This function has a nested loop.  The problem is that both the inside
and outside loop use the same variable as an iterator.  I found this
via static analysis so I'm not sure the impact.  It could be that it
loops forever or, more likely, the loop exits early.

Fixes: 3a616b92

 ("net: mvpp2: Add TX flow control support for jumbo frames")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/eaa8f403-7779-4d81-973d-a9ecddc0bf6f@stanley.mountain
Signed-off-by: Jakub Kicinski <kuba@kernel.org>