beacon_ie buffer is allocated in mwifiex_fill_new_bss_desc()
and the buffer pointer is saved in bss_desc->beacon_buf.
beacon_ie is freed before the function returns. However,
bss_desc->beacon_buf is still being accessed afterwards.

Fix it by freeing beacon_ie (bss_desc->beacon_buf) in
caller's scope.
Reviewed-by: NDoug Anderson <dianders@chromium.org>
Reviewed-by: NPaul Stewart <pstew@chromium.org>
Signed-off-by: NBing Zhao <bzhao@marvell.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>