media: vidtv: psi: Add check for kstrdup

Add check for the return value of kstrdup() and return the error
if it fails in order to avoid NULL pointer dereference.

Fixes: 7a7899f6 ("media: vidtv: psi: Implement an Event Information Table (EIT)")
Fixes: c2f78f0c ("media: vidtv: psi: add a Network Information Table (NIT)")
Fixes: f90cf607 ("media: vidtv: add a bridge driver")
Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>