tools: lib: thermal: don't preserve owner in install

Instead of preserving mode, timestamp, and owner, for the object files
during installation, just preserve the mode and timestamp.

When installing as root, the installed files should be owned by root.
When installing as user, --preserve=ownership doesn't work anyway. This
makes --preserve=ownership rather pointless.

Signed-off-by: Emil Dahl Juhl <juhl.emildahl@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>