remove explicit checks for BCM5716.
The BCM5709 and BCM5716 chips are virtually indistinguishable by
software except for the PCI device ID. The two chips differ in
that BCM5709 supports TCP/IP and iSCSI offload in Windows while
the BCM5716 doesn't.
While I'm here remove now unused definition of BCE_CHIP_NUM_5716
and BCE_CHIP_ID_5716_C0.
Reported by: sbruno
Reviewed by: davidch
Tested by: davidch