Unit tests: Add stubs for analogin_api.c functions

Currently there are no stub implementations of the analogin_api.c
functions. As the AnalogIn class makes use of these functions, these
stub definitions are required in order to build AnalogIn.cpp and
generate .gcno files to be used to generate code coverage metrics.

hal/tests/UNITTESTS/doubles/CMakeLists.txt

@@ -17,6 +17,7 @@ target_compile_definitions(mbed-stubs-hal
         DEVICE_PWMOUT
         DEVICE_WATCHDOG
         MBED_WDOG_ASSERT=1
+        DEVICE_ANALOGIN
 )
 
 target_sources(mbed-stubs-hal
@@ -24,6 +25,7 @@ target_sources(mbed-stubs-hal
         pwmout_api_stub.c
         us_ticker_stub.cpp
         watchdog_api_stub.c
+        analogin_api_stub.c
 )
 
 target_link_libraries(mbed-stubs-hal

hal/tests/UNITTESTS/doubles/analogin_api_stub.c

@@ -0,0 +1,49 @@
+/*
+ * Copyright (c) 2021 Arm Limited and affiliates.
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include "hal/analogin_api.h"
+#include <stddef.h>
+
+#if DEVICE_ANALOGIN
+
+void analogin_init_direct(analogin_t *obj, const PinMap *pinmap)
+{
+}
+
+void analogin_init(analogin_t *obj, PinName pin)
+{
+}
+
+void analogin_free(analogin_t *obj)
+{
+}
+
+float analogin_read(analogin_t *obj)
+{
+    return 0;
+}
+
+uint16_t analogin_read_u16(analogin_t *obj)
+{
+    return 0;
+}
+
+const PinMap *analogin_pinmap(void)
+{
+    return NULL;
+}
+
+#endif // DEVICE_ANALOGIN