[media] cx23885-dvb: move initialization of a8293_pdata

Smatch complains about where the au8293_data is placed:

drivers/media/pci/cx23885/cx23885-dvb.c:2174 dvb_register() info: 'a8293_pdata' is not actually initialized (unreached code).

It is not actually expected to have such initialization at

switch {
	foo = bar;

	case:
...
}

Not really sure how gcc does that, but this is something that I would
expect that different compilers would do different things.

David Howells checked with the compiler people: it's not really expected to
initialise as expected.

So, move the initialization outside the switch(), making smatch to
shut up one warning.

Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>