cfg80211: code rearrangement to avoid forward declarations

bss_release() and __cfg80211_unlink_bss() function definitions
are moved at the begining of the file. They are used in next
patch in this series.

Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>