thermal: hisi: Use kcalloc() instead of kzalloc() with multiplication

According to the latest recommendations, kcalloc() should be used
instead of kzalloc() with multiplication (which might overflow).

Switch to this new scheme and use more safe kcalloc().

No functional impact.

Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
Link: https://patch.msgid.link/20250224173432.1946070-5-lukasz.luba@arm.com


[ rjw: Changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>