ravb: fix shadowing of symbol 'stats' in ravb_get_ethtool_stats()

Inside a loop in ravb_get_ethtool_stats() a variable 'stats' is declared
resulting in the argument also named 'stats' to be shadowed. Fix this
warning by renaming the unused argument 'stats' to 'estats'.

This fixes the sparse warning:

ravb_main.c:1225:36: originally declared here
ravb_main.c:1233:41: warning: symbol 'stats' shadows an earlier one

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: David S. Miller <davem@davemloft.net>