mfd: tps65218: Fix reported randconfig error

Reported error was:
  ERROR: "regmap_del_irq_chip" [drivers/mfd/tps65218.ko] undefined!
    when CONFIG_REGMAP_IRQ is not enabled.

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>