[media] DVB: Less function calls in dvb_ca_en50221_init() after error detection

The functions "dvb_unregister_device" and "kfree" could still be called
by the dvb_ca_en50221_init() function in the case that a previous resource
allocation failed.

* Corresponding details could be improved by adjustments for jump targets.

* Let us delete also an unnecessary check for the variable "ca" there.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>