smsc911x: check for FFWD success before checking for timeout

This patch from Juha Leppanen suppresses a false warning if a fast
forward operation succeeds on the very last attempt.

Juha> If smsc911x_reg_read loop is executed 500 times, timeout reaches 0
Juha> and the 500th smsc911x_reg_read result in val is ignored. If
Juha> testing order is changed, then val is checked first. The 500th
Juha> reg_read might be GOOD, why ignore it!

Signed-off-by: Steve Glendinning <steve.glendinning@smsc.com>
Signed-off-by: David S. Miller <davem@davemloft.net>