[media] dvb-usb-v2: Fix cypress firmware compilation

ERROR: "usbv2_cypress_load_firmware" [drivers/media/dvb/dvb-usb-v2/dvb-usb-az6007.ko] undefined!

Cypress fimware will never be compiled properly, as the Makefile rule
is wrong.

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