pinctrl: mcp23s08: fix interrupt handling regression

interrupt handling was broken with conversion to using regmap caching.
cached_gpio value was updated by boolean status instead of gpio reading.

Fixes: 8f38910ba4f6 ("pinctrl: mcp23s08: switch to regmap caching")
Tested-by: Phil Reid <preid@electromag.com.au>
Signed-off-by: Dmitry Mastykin <mastichi@gmail.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/pinctrl-mcp23s08.c

@@ -407,10 +407,10 @@ static int mcp23s08_get(struct gpio_chip *chip, unsigned offset)
 	ret = mcp_read(mcp, MCP_GPIO, &status);
 	if (ret < 0)
 		status = 0;
-	else
+	else {
+		mcp->cached_gpio = status;
 		status = !!(status & (1 << offset));
-
-	mcp->cached_gpio = status;
+	}
 
 	mutex_unlock(&mcp->lock);
 	return status;