scsi: ufs: core: Validate string descriptors

In the Linux kernel, the following vulnerability has been resolved: scsi: ufs: core: Validate string descriptors The string descriptor length includes a two-byte header while the UTF-16 payload starts after it. utf16s_to_utf8s() expects a count of UTF-16 code units, not bytes. Passing the payload byte count can make it read beyond the descriptor buffer. Validate that the payload has an even byte count, pass a code-unit count to the converter, and allocate sufficient UTF-8 output space. The raw string buffer starts after the descriptor header but its size is bLength. Copying bLength bytes from that pointer can read beyond the response buffer. Allocate a zeroed bLength-sized buffer and copy only the UTF-16 payload. This preserves the raw buffer size consumed by the RPMB device-ID ABI while avoiding the overread.