drivers/char/ipmi: memcpy, need additional 2 bytes to avoid memory overflow

drivers/char/ipmi: memcpy, need additional 2 bytes to avoid memory overflow

When calling memcpy, read_data and write_data need additional 2 bytes.

  write_data:
    for checking:  "if (size > IPMI_MAX_MSG_LENGTH)"
    for operating: "memcpy(bt->write_data + 3, data + 1, size - 1)"

  read_data:
    for checking:  "if (msg_len < 3 || msg_len > IPMI_MAX_MSG_LENGTH)"
    for operating: "memcpy(data + 2, bt->read_data + 4, msg_len - 2)"

Signed-off-by: Chen Gang <[email protected]>
Signed-off-by: Corey Minyard <[email protected]>
Cc: [email protected]
Signed-off-by: Linus Torvalds <[email protected]>