mwifiex: correct bitrates advertised to cfg80211

1. Driver and firmware do not support 22Mbps and 72Mbps bitrates.
Remove them from the rate table advertised to cfg80211.

2. First 4 rates from mwifiex_rates table are not valid for
5GHz/A band. Set correct bitrate array's index and no of rates for
ieee80211_supported_band for 5GHz band.

Signed-off-by: Avinash Patil <patila@marvell.com>
Signed-off-by: Nishant Sarmukadam <nishants@marvell.com>
Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Yogesh Ashok Powar <yogeshp@marvell.com>
Signed-off-by: Kiran Divekar <dkiran@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>