media: vidtv: mux: Add check and kfree for kstrdup

media: vidtv: mux: Add check and kfree for kstrdup

[ Upstream commit 1fd6eb12642e0c32692924ff359c07de4b781d78 ]

Add check for the return value of kstrdup() and return the error
if it fails in order to avoid NULL pointer dereference.
Moreover, use kfree() in the later error handling in order to avoid
memory leak.

Fixes: c2f78f0cb294 ("media: vidtv: psi: add a Network Information Table (NIT)")
Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Sasha Levin <sashal@kernel.org>