adc: 解决bug84921

Change-Id: I313c6a218acf3a41621ec9cc87343736afbd70dc
diff --git a/mbtk/liblynq_lib/src/lynq_adc.c b/mbtk/liblynq_lib/src/lynq_adc.c
index aae9373..4317e17 100755
--- a/mbtk/liblynq_lib/src/lynq_adc.c
+++ b/mbtk/liblynq_lib/src/lynq_adc.c
@@ -9,6 +9,10 @@
 
     mbtk_adc_enum adc = MBTK_ADC0;
     switch(qadc) {
+        case QADC_NONE:
+        {
+            return 0;
+        }
         case ADC0:
             adc = MBTK_ADC0;
             break;
@@ -18,6 +22,7 @@
 #if defined(MBTK_PROJECT_T108) || defined(MBTK_PROJECT_L508_X6)
         case ADC2:
             adc = MBTK_ADC2;
+            break;
 #endif
         default:
             LOGE("Unsupport adc : %d", qadc);