mwifiex: merge functions to derive cfp by chan & freq in one

There exist different functions with very long names
to derive the channel frequency and power tripplet
based on band and channel/freq.

Signed-off-by: Yogesh Ashok Powar <yogeshp@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>