vt6656: Use request_firmware() to load firmware

The file added to linux-firmware is a copy of the current array which
does not have a recognisable header, so no validation is done.

Change the firmware version check to accept newer versions.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>