rt2x00: correctly set max_report_rates in rt61pci and rt2800

rt61pci and rt2800 devices can use up to 7 different rates per tx frame.
However, the device uses a global fallback table. Hence, the rc
algortihm cannot specify multiple rates to try but the device is able to
report multiple rates (based on the retry table). Specify that behavior
by correctly setting max_report_rates and max_rates.

This makes rt2x00 and minstrel play nicer together.

Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>