mwifiex: use cfg80211 dynamic scan table and cfg80211_get_bss API

Instead of maintaining static scan table in driver, scan list is sent
to cfg80211 stack (after parsing each scan command response).
In assoc handler (for infra and ibss network) requested BSS information
is retrieved using cfg80211_get_bss() API.

With the changes above some redundant code are removed.

Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
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>