Remove analogin_s definition from objects.h

The structure being already defined in
targets/TARGET_STM/TARGET_STM32L4/common_objects.h#L119, there is a
redefinition conflict.

Author: Nabil Elqatib

targets/TARGET_STM/TARGET_STM32L4/TARGET_STM32L496xG/objects.h

@@ -54,12 +54,6 @@ struct port_s {
     __IO uint32_t *reg_out;
 };
 
-struct analogin_s {
-    ADCName adc;
-    PinName pin;
-    uint32_t channel;
-};
-
 struct can_s {
     CANName can;
     int index;