staging: ath6kl: buffer overflow in SEND_FRAME ioctl

We should check that optTxFrmCmd.optIEDataLen isn't too large before we
copy it into the data buffer.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Acked-by: Vipin Mehta <vipin.mehta@atheros.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>