staging: crystalhd: remove driver

The driver hasn't had significant work done on it for a long time.
Broadcom has EOLed the hardware and is no longer selling it. There are
probably very few people still using it. So remove the driver.

Signed-off-by: Kristina Martšenko <kristina.martsenko@gmail.com>
Cc: Naren Sankar <nsankar@broadcom.com>
Cc: Jarod Wilson <jarod@wilsonet.com>
Cc: Scott Davilla <davilla@4pi.com>
Cc: Manu Abraham <abraham.manu@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>