mwifiex: add calibration data download feature

User can provide a text file containing calibration data in hex
format while loading mwifiex module. It will be downloaded to
firmware.
eg. insmod mwifiex.ko cal_data_cfg=cal_data.conf

Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>