thermal: intel: powerclamp: Fix NULL pointer access issue

thermal: intel: powerclamp: Fix NULL pointer access issue

If cur_state for the powerclamp cooling device is set to the default
minimum state of 0, without setting first to cur_state > 0, this results
in NULL pointer access.

This NULL pointer access happens in the powercap core idle-inject
function idle_inject_set_duration() as there is no NULL check for
idle_inject_device pointer. This pointer must be allocated by calling
idle_inject_register() or idle_inject_register_full().

In the function powerclamp_set_cur_state(), idle_inject_device pointer
is allocated only when the cur_state > 0. But setting 0 without changing
to any other state, idle_inject_set_duration() will be called with a
NULL idle_inject_device pointer.

To address this, just return from powerclamp_set_cur_state() if the
current cooling device state is the same as the last one. Since the
power-up default cooling device state is 0, changing the state to 0
again here will return without calling idle_inject_set_duration().

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Fixes: 8526eb7fc75a ("thermal: intel: powerclamp: Use powercap idle-inject feature")
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=217386
Tested-by: Risto A. Paju <teknohog@iki.fi>
Cc: 6.3+ <stable@kernel.org> # 6.3+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>