Disable platforms not supporting new RTC

Author: bulislaw

targets/targets.json

@@ -2851,7 +2851,7 @@
         "macros": ["__SYSTEM_HFX=96000000","TARGET=MAX32620","TARGET_REV=0x4332","OPEN_DRAIN_LEDS"],
         "extra_labels": ["Maxim", "MAX32620C"],
         "supported_toolchains": ["GCC_ARM", "IAR", "ARM"],
-        "device_has": ["ANALOGIN", "I2C", "INTERRUPTIN", "LPTICKER", "PORTIN", "PORTINOUT", "PORTOUT", "PWMOUT", "RTC", "SERIAL", "SERIAL_FC", "SLEEP", "SPI", "STDIO_MESSAGES", "USTICKER"],
+        "device_has": ["ANALOGIN", "I2C", "INTERRUPTIN", "LPTICKER", "PORTIN", "PORTINOUT", "PORTOUT", "PWMOUT", "SERIAL", "SERIAL_FC", "SLEEP", "SPI", "STDIO_MESSAGES", "USTICKER"],
         "release_versions": ["2", "5"]
     },
     "MAX32625_BASE": {