tools/thermal/thermal-engine: Fix format string bug in thermal-engine

The error message in the daemon() failure path uses %p format specifier
without providing a corresponding pointer argument, resulting in undefined
behavior and printing garbage values.

Replace %p with %m to properly print the errno error message, which is
the intended behavior when daemon() fails.

This fix ensures proper error reporting when daemonization fails.

Signed-off-by: Malaya Kumar Rout <mrout@redhat.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://patch.msgid.link/20251124104401.374856-1-mrout@redhat.com