Fix a regression introduced in r213495. r213495 disabled mini
receive producer ring only for BCM5700. It was believed that
BCM5700 with external SSRAM is the only controller that supports
mini ring but it seems all BCM570[0-4] requires to disable mini
receive producer ring. Otherwise, it caused unexpected RX DMA
error or watchdog timeouts.

Reported by: marius, Steve Kargl <sgk <> troutmask dot apl dot washington dot edu>
Tested by: marius, Steve Kargl <sgk <> troutmask dot apl dot washington dot edu>