fix bugs in animation effects

quantum/rgblight.c

@@ -445,7 +445,7 @@ void rgblight_effect_snake(uint8_t interval) {
 	rgblight_set();
 	if (increament == 1) {
 		if (pos - 1 < 0) {
-			pos = 13;
+			pos = RGBLED_NUM-1;
 		} else {
 			pos -= 1;
 		}

quantum/rgblight.h

@@ -13,7 +13,7 @@
 #define RGBLIGHT_EFFECT_KNIGHT_LENGTH 7
 #endif
 #ifndef RGBLIGHT_EFFECT_KNIGHT_OFFSET
-#define RGBLIGHT_EFFECT_KNIGHT_OFFSET 11
+#define RGBLIGHT_EFFECT_KNIGHT_OFFSET 9
 #endif
 
 #ifndef RGBLIGHT_EFFECT_DUALKNIGHT_LENGTH