[media] ad9389b: driver for the Analog Devices AD9389B video encoder

[media] ad9389b: driver for the Analog Devices AD9389B video encoder

Initial version of this driver.

The full datasheets are available from the Analog Devices website:

  http://ez.analog.com/docs/DOC-1741

Not all features of the receiver are supported by this driver for various
reasons. Most notably:

- No CEC support (the CEC API needs a lot more discussion)
- No HDCP repeater support (we don't use that either)

I'm sure that there are more things missing, but this driver does work
well for our hardware.

Note that I am using the register addresses instead of register names: the
datasheet containing the register descriptions is organized by register
address. Using names would make the datasheet lookup very hard. An attempt
was made to try and document what is being done when registers are used
instead.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>