[M453] Fix CI tests-api-analogin failed

1. Fix ADC convert finish check error.
2. Set ADC Vref to internal by default.

Author: ccli8

targets/TARGET_NUVOTON/TARGET_M451/TARGET_NUMAKER_PFM_M453/mbed_overrides.c

@@ -64,9 +64,8 @@ void mbed_sdk_init(void)
     CLK_SetCoreClock(72000000);
 
 #if DEVICE_ANALOGIN
-    // FIXME: Check voltage reference for EADC
-    /* Vref connect to AVDD */
-    //SYS->VREFCTL = (SYS->VREFCTL & ~SYS_VREFCTL_VREFCTL_Msk) | SYS_VREFCTL_VREF_AVDD;
+    /* Vref connect to internal */
+    SYS->VREFCTL = (SYS->VREFCTL & ~SYS_VREFCTL_VREFCTL_Msk) | SYS_VREFCTL_VREF_3_072V;
 #endif
 
     /* Update System Core Clock */

targets/TARGET_NUVOTON/TARGET_M451/analogin_api.c

@@ -141,7 +141,7 @@ uint16_t analogin_read_u16(analogin_t *obj)
     uint32_t chn =  NU_MODSUBINDEX(obj->adc);
 
     EADC_START_CONV(eadc_base, 1 << chn);
-    while (EADC_GET_PENDING_CONV(eadc_base) & (1 << chn));
+    while (EADC_GET_DATA_VALID_FLAG(eadc_base, 1 << chn) != (1 << chn));
     uint16_t conv_res_12 = EADC_GET_CONV_DATA(eadc_base, chn);
     // Just 12 bits are effective. Convert to 16 bits.
     // conv_res_12: 0000 b11b10b9b8 b7b6b5b4 b3b2b1b0