V4L/DVB (6647): xc2028: retry firmware load if tuner does not respond

In practice, the tuner occasionally fails to respond correctly after a
firmware load.  Retry the firmware load if the firmware/hardware version
we read back from the tuner after programming does not match what we
expect.

Signed-off-by: Chris Pascoe <c.pascoe@itee.uq.edu.au>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>