staging/crystalhd: unregister chardev when class_create fails in chd_dec_init_chdev

we missed a unregiser_chrdev if the class_create and subsequent function calls / checks fail

Signed-off-by: Devendra Naga <develkernel412222@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>