pinctrl: samsung: dt-bindings: Use better name for external interrupt function

On Exynos, 0xf is always used as value of external interrupt in pin mux
function thus a more descriptive macro name can be used.
Signed-off-by: NKrzysztof Kozlowski <krzk@kernel.org>

include/dt-bindings/pinctrl/samsung.h

@@ -66,7 +66,8 @@
 #define EXYNOS_PIN_FUNC_4		4
 #define EXYNOS_PIN_FUNC_5		5
 #define EXYNOS_PIN_FUNC_6		6
-#define EXYNOS_PIN_FUNC_F		0xf
+#define EXYNOS_PIN_FUNC_EINT		0xf
+#define EXYNOS_PIN_FUNC_F		EXYNOS_PIN_FUNC_EINT
 
 /* Drive strengths for Exynos7 FSYS1 block */
 #define EXYNOS7_FSYS1_PIN_DRV_LV1	0