[media] cypress_firmware: refactor firmware downloading

Refactor firmware download function. It also should fix one bug
coming from usb_control_msg() message buffers. Taking buffers from
the stack for usb_control_msg() is not allowed as it does not work
on all architectures. Allocate buffers using kmalloc().

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