h8300: Fix linux/irqchip.h include mess

h8300 drags linux/irqchip.h from asm/irq.h, which is in general a bad
idea (asm/*.h should avoid dragging linux/*.h, as it is usually supposed
to work the other way around).

Move the inclusion of linux/irqchip.h to the single location where it
actually matters in the arch code.

Reported-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211028172849.GA701812@roeck-us.net