pinctrl: qcom: Allow SoCs to specify a GPIO function that's not 0

There's currently a comment in the code saying function 0 is GPIO.
Instead of hardcoding it, let's add a member where an SoC can specify
it. No known SoCs use a number other than 0, but this just makes the
code clearer. NOTE: no SoC code needs to be updated since we can rely
on zero-initialization.

Signed-off-by: Douglas Anderson <[e-mail]>
Reviewed-by: Stephen Boyd <[e-mail]>
Reviewed-by: Maulik Shah <[e-mail]>
Tested-by: Maulik Shah <[e-mail]>
Reviewed-by: Bjorn Andersson <[e-mail]>
Link: https://lore.kernel.org/r/20210114191601.v7.1.I3ad184e3423d8e479bc3e86f5b393abb1704a1d1@changeid
Signed-off-by: Linus Walleij <[e-mail]>

drivers/pinctrl/qcom/pinctrl-msm.c

···
 	if (!g->nfuncs)
 		return 0;
 
-	/* For now assume function 0 is GPIO because it always is */
-	return msm_pinmux_set_mux(pctldev, g->funcs[0], offset);
+	return msm_pinmux_set_mux(pctldev, g->funcs[pctrl->soc->gpio_func], offset);
 }
 
 static const struct pinmux_ops msm_pinmux_ops = {

drivers/pinctrl/qcom/pinctrl-msm.h

···
  * @wakeirq_dual_edge_errata: If true then GPIOs using the wakeirq_map need
  *                            to be aware that their parent can't handle dual
  *                            edge interrupts.
+ * @gpio_func: Which function number is GPIO (usually 0).
  */
 struct msm_pinctrl_soc_data {
 	const struct pinctrl_pin_desc *pins;
···
 	const struct msm_gpio_wakeirq_map *wakeirq_map;
 	unsigned int nwakeirq_map;
 	bool wakeirq_dual_edge_errata;
+	unsigned int gpio_func;
 };
 
 extern const struct dev_pm_ops msm_pinctrl_dev_pm_ops;