pinctrl: stm32: consider the GPIO offset to expose all the GPIO lines

Consider the GPIO controller offset (from "gpio-ranges") to compute the
maximum GPIO line number.
This fixes an issue where gpio-ranges uses a non-null offset.
e.g.: gpio-ranges = <&pinctrl 6 86 10>
In that case the last valid GPIO line is not 9 but 15 (6 + 10 - 1)

Cc: [e-mail]
Fixes: 67e2996f72c7 ("pinctrl: stm32: fix the reported number of GPIO lines per bank")
Reported-by: Christoph Fritz <[e-mail]>
Signed-off-by: Fabien Dessenne <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Linus Walleij <[e-mail]>

drivers/pinctrl/stm32/pinctrl-stm32.c

···
 		bank_nr = args.args[1] / STM32_GPIO_PINS_PER_BANK;
 		bank->gpio_chip.base = args.args[1];
 
-		npins = args.args[2];
-		while (!of_parse_phandle_with_fixed_args(np, "gpio-ranges", 3,
-							 ++i, &args))
-			npins += args.args[2];
+		/* get the last defined gpio line (offset + nb of pins) */
+		npins = args.args[0] + args.args[2];
+		while (!of_parse_phandle_with_fixed_args(np, "gpio-ranges", 3, ++i, &args))
+			npins = max(npins, (int)(args.args[0] + args.args[2]));
 	} else {
 		bank_nr = pctl->nbanks;
 		bank->gpio_chip.base = bank_nr * STM32_GPIO_PINS_PER_BANK;