staging: rtl8723bs: fix stack buffer overflow in OnAssocReq IE parsing

In the Linux kernel, the following vulnerability has been resolved: staging: rtl8723bs: fix stack buffer overflow in OnAssocReq IE parsing The Supported Rates IE length from an incoming Association Request frame was used directly as the memcpy() length when copying into a fixed-size 16-byte stack buffer (supportRate). A malicious station can advertise an IE length larger than 16 bytes, causing a stack buffer overflow. Clamp ie_len to the buffer size before copying the Supported Rates IE, and correct the bounds check when merging Extended Supported Rates to prevent a second potential overflow. This prevents kernel stack corruption triggered by malformed association requests.