gpio: atmel_pio4: add drive strength macros

Macros for drive strength configuration were missing.

Signed-off-by: Ludovic Desroches <ludovic.desroches@microchip.com>

arch/arm/mach-at91/include/mach/atmel_pio4.h

@@ -47,6 +47,10 @@ struct atmel_pio4_port {
 #define ATMEL_PIO_IFSCEN_MASK		BIT(13)
 #define ATMEL_PIO_OPD_MASK		BIT(14)
 #define ATMEL_PIO_SCHMITT_MASK		BIT(15)
+#define ATMEL_PIO_DRVSTR_MASK		GENMASK(17, 16)
+#define ATMEL_PIO_DRVSTR_LO		(1 << 16)
+#define ATMEL_PIO_DRVSTR_ME		(2 << 16)
+#define ATMEL_PIO_DRVSTR_HI		(3 << 16)
 #define ATMEL_PIO_CFGR_EVTSEL_MASK	GENMASK(26, 24)
 #define ATMEL_PIO_CFGR_EVTSEL_FALLING	(0 << 24)
 #define ATMEL_PIO_CFGR_EVTSEL_RISING	(1 << 24)