[PATCH 3.16 087/134] staging: rtl8188eu: prevent an underflow in rtw_check_beacon_data()

3.16.47-rc1 review patch. If anyone has any objections, please let me know. -- From: Dan Carpenter commit 784047eb2d3405a35087af70cba46170c5576b25 upstream. The "len" could be as low as -14 so we should check for negatives. Fixes: 9a7fe54ddc3a

[PATCH 3.16 087/134] staging: rtl8188eu: prevent an underflow in rtw_check_beacon_data()

3.16.47-rc1 review patch. If anyone has any objections, please let me know. -- From: Dan Carpenter commit 784047eb2d3405a35087af70cba46170c5576b25 upstream. The "len" could be as low as -14 so we should check for negatives. Fixes: 9a7fe54ddc3a ("staging: r8188eu: Add source