M467: Support NuMaker-IoT-M467 board

Pinout comparison between NuMaker-M467HJ and NuMaker-IoT-M467 boards:
1.  UNO are unchanged
2.  LEDs are unchanged
3.  Buttons are unchanged, except button names
4.  NuMaker-M467HJ has HBI but NuMaker-IoT-M467 does
5.  NuMaker-M467HJ doesn't have ESP8266 but NuMaker-IoT-M467 does
6.  SDHC are unchanged

Author: ccli8

targets/TARGET_NUVOTON/TARGET_M460/TARGET_NUMAKER_IOT_M467/PinNames.h

@@ -97,10 +97,10 @@ typedef enum {
 #define LED3        PH_6    // LED_GREEN
 
 // Button naming
-#define BUTTON1     PH_0    // SW2
-#define BUTTON2     PH_1    // SW3
-#define SW2         BUTTON1
-#define SW3         BUTTON2
+#define BUTTON1     PH_0    // BTN0
+#define BUTTON2     PH_1    // BTN1
+#define BTN0        BUTTON1
+#define BTN1        BUTTON2
 
 #ifdef __cplusplus
 }