V4L/DVB (7530): budget-av: Fix support for certain cams

The current ci implementation doesn't accept 0xff when reading data bytes (address == 0),
thus breaks cams which report a buffer size of 0x--ff like my orion one.
Remove the 0xff check altogether, because validation is really the job of a higher layer.

Signed-off-by: Christoph Pfister <pfister@linuxtv.org>
Signed-off-by: Oliver Endriss <o.endriss@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>