Input: mt6779-keypad - fix signedness bug

The irq variable is defined as unsigned int. If the platform_get_irq()
returns a negative value, data type cast may result in error.

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Lv Ruyi (CGEL ZTE) <lv.ruyi@zte.com.cn>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Link: https://lore.kernel.org/r/20220308025054.2077162-1-lv.ruyi@zte.com.cn
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Author: Lv Ruyi (CGEL ZTE)

drivers/input/keyboard/mt6779-keypad.c

@@ -91,7 +91,7 @@ static void mt6779_keypad_clk_disable(void *data)
 static int mt6779_keypad_pdrv_probe(struct platform_device *pdev)
 {
 	struct mt6779_keypad *keypad;
-	unsigned int irq;
+	int irq;
 	u32 debounce;
 	bool wakeup;
 	int error;