Add SERIAL_FC in targets.json/device_has field for NUCLEO_F103RB

Author: bcostm

targets/targets.json

@@ -721,7 +721,7 @@
         "inherits": ["Target"],
         "detect_code": ["0700"],
         "macros": ["TRANSACTION_QUEUE_SIZE_SPI=2"],
-        "device_has": ["ANALOGIN", "CAN", "I2C", "I2CSLAVE", "INTERRUPTIN", "PORTIN", "PORTINOUT", "PORTOUT", "PWMOUT", "RTC", "SERIAL", "SERIAL_ASYNCH", "SLEEP", "SPI", "SPISLAVE", "SPI_ASYNCH", "STDIO_MESSAGES"],
+        "device_has": ["ANALOGIN", "CAN", "I2C", "I2CSLAVE", "INTERRUPTIN", "PORTIN", "PORTINOUT", "PORTOUT", "PWMOUT", "RTC", "SERIAL", "SERIAL_FC", "SERIAL_ASYNCH", "SLEEP", "SPI", "SPISLAVE", "SPI_ASYNCH", "STDIO_MESSAGES"],
         "release_versions": ["2", "5"],
         "device_name": "STM32F103RB"
     },