tg3: Obtain PCI function number from device

tg3: Obtain PCI function number from device

This patch adds code to attempt to obtain the PCI function number from
the device rather than accept the number handed by the kernel.  In
pass-through scenarios, the function number handed by the kernel may not
reflect the true function of the device.

(cherry picked from commit 9dc5e342703948ea7b086d063c85c0e79dac8149)
Signed-off-by: Matt Carlson <mcarlson@broadcom.com>
Reviewed-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Joe Jin <joe.jin@oracle.com>