p54: report appropriate rate and band values for 802.11a

This patch adds the a few lines that went missing in
"p54: 802.11a 5GHz phy support"

Essentially: the rx-code wasn't updated and therefore reported the wrong band,
but more importantly the rate index was off as well, since 802.11a doesn't
allow the "four" 802.11b rates...

Signed-off-by: Christian Lamparter <chunkeey@web.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>