sh_eth: kill redundant check in the probe() method

Browsing thru the driver disassembly, I noticed that gcc was  able to
figure  out  that the 'ndev' pointer is always non-NULL when calling
free_netdev()  on the probe() method's  error path and  thus skip that
redundant NULL check... gcc is smart, be like gcc! :-)

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