[fix] fix pinmux_init and while(1) process

examples/pwm/pwm_breath_led/main.c

@@ -63,6 +63,4 @@ int main(void)
             bflb_platform_delay_ms(10);
         }
     }
-
-    BL_CASE_SUCCESS;
 }

examples/pwm/pwm_it/main.c

@@ -52,7 +52,6 @@ int main(void)
 
     while (1)
     {
+        __asm volatile ("nop");
     }
-
-    BL_CASE_SUCCESS;
 }

examples/systick/main.c

@@ -36,6 +36,7 @@ int main(void)
     bflb_platform_set_alarm_time(1000000,systick_isr);
     while(1)
     {   
+        __asm volatile ("nop");
     } 
 }
 

examples/uart/uart_echo/main.c

@@ -46,5 +46,9 @@ int main(void)
         device_control(uart, DEVICE_CTRL_SET_INT, (void *)(UART_RX_FIFO_IT|UART_RTO_IT));
     }
 
-    BL_CASE_SUCCESS;
+    while (1)
+    {
+       __asm volatile ("nop");
+    }
+    
 }