Disable ESP8266 support

Without a working RTC slew functionality the ESP8266
support makes no sense.

Author: wieck

README.md

@@ -1,24 +1,21 @@
 micropython-ntpclient
 =====================
 
-A uasyncio based NTP client for ESP32/ESP8266 boards running micropython.
+A uasyncio based NTP client for ESP32 boards running micropython.
 
 **At this moment this code only works on boards with a custom build
 micropython firmware.**
 
 Please go to https://forum.micropython.org/viewtopic.php?f=15&t=7567
 for discussion and questions. 
 
-**The following commits were never accepted by the upstream project.
-In order to make the utime.adjtime() available please apply the
+**The following commit was never accepted by the upstream project.
+In order to make the utime.adjtime() function available please apply the
 included patch _esp32_adjtime.diff_ and build a custom micropython image.**
 
 ~~Required commit to be cherry-picked for ESP32: 
 https://github.com/wieck/micropython/commit/cd80a9aba99a68af7e295067fa7d35383ccef640~~
 
-~~Required commit to be cherry-picked for ESP8266: 
-https://github.com/wieck/micropython/commit/97e58630e74b024b58aeb5964d104973b361cad5~~
-
 
 Installation and testing
 ------------------------

ntpclient/__init__.py

@@ -2,7 +2,5 @@
 
 if platform == 'esp32':
     from .ntpclient_esp32 import *
-elif platform == 'esp8266':
-    from .ntpclient_esp8266 import *
 else:
     raise Exception("unsupported platform '{}'".format(platform))

ntpclient/ntpclient_esp8266.py

@@ -1,5 +1,11 @@
 # ntpclient_esp8266.py
 
+########################################################################
+# WARNING: This part of the ntpclient package is not maintained at this
+# point. The original functionality to slew the ESP8266 RTC was not
+# working reliable.
+########################################################################
+
 import os
 import usocket as socket
 import ustruct as struct