Minor code cleanup in drivers/net/r6040.c

Replaced '0' by 'bar' in the probe function.

The 'bar' variable was already set to '0' and is already
used in pci_iomap(). This is cleaner and improves code
consistency.

Signed-off-by: Michael Opdenacker <michael@free-electrons.com>
Acked-by: Florian Fainelli <florian@openwrt.org>
Signed-off-by: David S. Miller <davem@davemloft.net>