[media] dvb_usb_v2: clean firmware downloading routines

Remove Cypress USB-interface firmware downloading routines.
That is common module and having single vendor chip routines
in common module is wrong. Just move those elsewhere.

Move single function out from the dvb_usb_firmware.c and
remove that file.

Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>