media: tm6000: add error handling for dvb_register_adapter

When dvb_register_adapter fails, the lack of error-handling code may
cause unexpected results.

This patch adds error-handling code after calling dvb_register_adapter.

Signed-off-by: Zhouyang Jia <jiazhouyang09@gmail.com>
[hans.verkuil@cisco.com: use pr_err and fix typo: adater -> adapter]
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>