of: base: use strscpy() to instead of strncpy()

The implementation of strscpy() is more robust and safer.
That's now the recommended way to copy NUL terminated strings.

Signed-off-by: Xu Panda <xu.panda@zte.com.cn>
Signed-off-by: Yang Yang <yang.yang29@zte.com>
Link: https://lore.kernel.org/r/202212231039128402297@zte.com.cn


Signed-off-by: Rob Herring <robh@kernel.org>