media: replace strncpy() by strscpy()

The strncpy() function is being deprecated upstream. Replace
it by the safer strscpy().

While here, replace a few occurences of strlcpy() that were
recently added to also use strscpy().

Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>