implement ergodox_left_leds_update in ergodox_ez

Previously, this code was implemented in keymap.c, but I'm unaware of
someone with a different implementation of this particular hack. [If
someone has it, we can add another #ifdef in the future.]

keyboards/ergodox_ez/ergodox_ez.c

@@ -151,6 +151,40 @@ out:
     return mcp23018_status;
 }
 
+#ifdef LEFT_LEDS
+uint8_t ergodox_left_leds_update(void) {
+    if (mcp23018_status) { // if there was an error
+        return mcp23018_status;
+    }
+#define LEFT_LED_1_SHIFT        7       // in MCP23018 port B
+#define LEFT_LED_2_SHIFT        6       // in MCP23018 port B
+#define LEFT_LED_3_SHIFT        7       // in MCP23018 port A
+
+    // set logical value (doesn't matter on inputs)
+    // - unused  : hi-Z : 1
+    // - input   : hi-Z : 1
+    // - driving : hi-Z : 1
+    mcp23018_status = i2c_start(I2C_ADDR_WRITE);
+    if (mcp23018_status) goto out;
+    mcp23018_status = i2c_write(OLATA);
+    if (mcp23018_status) goto out;
+    mcp23018_status = i2c_write(0b11111111
+                                & ~(ergodox_left_led_3<<LEFT_LED_3_SHIFT)
+                                );
+    if (mcp23018_status) goto out;
+    mcp23018_status = i2c_write(0b11111111
+                                & ~(ergodox_left_led_2<<LEFT_LED_2_SHIFT)
+                                & ~(ergodox_left_led_1<<LEFT_LED_1_SHIFT)
+                                );
+    if (mcp23018_status) goto out;
+
+ out:
+    i2c_stop();
+    return mcp23018_status;
+}
+#endif
+
+
 #ifdef ONEHAND_ENABLE
 __attribute__ ((weak))
 // swap-hands action needs a matrix to define the swap