bnx2x: Set ethtool ops for vfs

Virtual functions don't have access to HW registers, therefore most ethtool ops
are forbidden to them. Instead of checking in each op whether the device being
driven is a virtual function or a physical function, this patch creates a
separate ethtool ops struct for virtual functions and uses it to initialize
the ethtool ops of the driver in case it is driving a virtual function device.

Signed-off-by: Ariel Elior <ariele@broadcom.com>
Signed-off-by: Yuval Mintz <yuvalmin@broadcom.com>
Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>