net: ethernet: ti: am65-cpsw: Fix uninitialized variable

The *ndev pointer needs to be set or it leads to an uninitialized variable
bug in the caller.

Fixes: 4a7b2ba9 ("net: ethernet: ti: am65-cpsw: Use tstats instead of open coded version")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Roger Quadros <rogerq@kernel.org>
Message-ID: <b168d5c7-704b-4452-84f9-1c1762b1f4ce@stanley.mountain>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>