Helix config refine (#3374)

* helix config.h refine

keyboards/helix/rev1/serial_config.h

@@ -0,0 +1,16 @@
+#ifndef SOFT_SERIAL_CONFIG_H
+#define SOFT_SERIAL_CONFIG_H
+
+/* Soft Serial defines */
+#define SERIAL_PIN_DDR DDRD
+#define SERIAL_PIN_PORT PORTD
+#define SERIAL_PIN_INPUT PIND
+#define SERIAL_PIN_MASK _BV(PD0)
+#define SERIAL_PIN_INTERRUPT INT0_vect
+
+#define SERIAL_SLAVE_BUFFER_LENGTH MATRIX_ROWS/2
+#define SERIAL_MASTER_BUFFER_LENGTH 1
+
+/// #error rev1 serial config
+
+#endif /* SOFT_SERIAL_CONFIG_H */