x86/irq/i8259: Fix kernel-doc annotation warning

Fix this warning:

  arch/x86/kernel/i8259.c:235: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
   * ELCR registers (0x4d0, 0x4d1) control edge/level of IRQ
    CC      arch/x86/kernel/irqinit.o

Signed-off-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230830131211.88226-1-vincenzopalazzodev@gmail.com