tulip: windbond-840: Fix a debug message

'w89c840_open()' is incorrectly reported in a debug message. Use __func__
instead.

While at it, fix some style issue in the same function.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>