x86/irq: Add missing 's' back to thermal event printout

x86/irq: Add missing 's' back to thermal event printout

The /proc/interrupt handling rework dropped a 's' in the thermal event
printout, which breaks the thermal test in the Intel LKVS suite.

Bring the important letter back.

Fixes: 2b57c69917ee ("x86/irq: Make irqstats array based")
Reported-by: kernel test robot <oliver.sang@intel.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Closes: https://lore.kernel.org/oe-lkp/202606121325.97b29701-lkp@intel.com