net: wireless: bcmdhd: Verify SSID length (part deux)

Ensure SSID length is checked unsigned maximum

CVE-2016-2493
Bug: 26571522
Bug: 27240072

Signed-off-by: Mark Salyzyn <salyzyn@google.com>
Change-Id: I6cf37634e3a21eac6a90049a2dcc2912345f77f9