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 <[e-mail]>
Signed-off-by: Lv Ruyi (CGEL ZTE) <[e-mail]>
Reviewed-by: Mattijs Korpershoek <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Dmitry Torokhov <[e-mail]>

drivers/input/keyboard/mt6779-keypad.c

···
 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;