pinctrl/stm32: Add irq_eoi for stm32gpio irqchip

-Parent domain of stm32gpio evolves to hierarchy domain
 and could have a handle_fasteoi_irq. So an irq_eoi parent callback
 is needed for children.
-Replace space by tabulation.

Signed-off-by: Ludovic Barre <ludovic.barre@st.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>