pinctrl: microchip-sgpio: don't do RMW for interrupt ack register

The interrupt ack register has the usual "write one to clear" semantics.
No read-modify-write is required here.

This is also a preparation patch to change the sgpio_clrsetbits() to use
regmap_update_bits() which don't write the value if it is not changed.

Signed-off-by: Michael Walle <michael@walle.cc>
Link: https://lore.kernel.org/r/20220226204507.2511633-3-michael@walle.cc
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/pinctrl-microchip-sgpio.c

@@ -639,7 +639,14 @@ static void microchip_sgpio_irq_unmask(struct irq_data *data)
 
 static void microchip_sgpio_irq_ack(struct irq_data *data)
 {
-	microchip_sgpio_irq_setreg(data, REG_INT_ACK, false);
+	struct gpio_chip *chip = irq_data_get_irq_chip_data(data);
+	struct sgpio_bank *bank = gpiochip_get_data(chip);
+	unsigned int gpio = irqd_to_hwirq(data);
+	struct sgpio_port_addr addr;
+
+	sgpio_pin_to_addr(bank->priv, gpio, &addr);
+
+	sgpio_writel(bank->priv, BIT(addr.port), REG_INT_ACK, addr.bit);
 }
 
 static int microchip_sgpio_irq_set_type(struct irq_data *data, unsigned int type)