Remove support for the RTC

Only early versions of the interface firmware provided a clock for the RTC that was used. This has long been depreciated since it also routed the same pin to an ADC on the arduino connector which caused wiring conflicts

Author: sg-

hal/targets.json

@@ -428,7 +428,7 @@
         "progen": {
             "target": "frdm-kl05z"
         },
-        "device_has": ["ANALOGIN", "ANALOGOUT", "ERROR_RED", "I2C", "I2CSLAVE", "INTERRUPTIN", "PORTIN", "PORTINOUT", "PORTOUT", "PWMOUT", "RTC", "SEMIHOST", "SERIAL", "SLEEP", "SPI", "SPISLAVE", "STDIO_MESSAGES"],
+        "device_has": ["ANALOGIN", "ANALOGOUT", "ERROR_RED", "I2C", "I2CSLAVE", "INTERRUPTIN", "PORTIN", "PORTINOUT", "PORTOUT", "PWMOUT", "SEMIHOST", "SERIAL", "SLEEP", "SPI", "SPISLAVE", "STDIO_MESSAGES"],
         "default_build": "small"
     },
     "KL25Z": {