mfd: Use dummy_irq_chip for tc3589x

This also converts tc3589x to the new irq API.

Cc: Rabin Vincent <rabin.vincent@stericsson.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>