V4L/DVB (4648): Hauppauge Nova-T 500 support added

This changeset finalizes the support of the Hauppauge Nova-T 500 (Dual DVB-T).
It adds correct AGC setting for the 3000P, correct firmware download state
detection.
Additionally it fixes the mt2060-driver to be able to be used with dvb_attach.

Signed-off-by: Patrick Boettcher <pb@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>