[nrf fromtree] modules: openthread: fix multiple definition in openthread config

remove `CONFIG_OPENTHREAD_RADIO_LINK_IEEE_802_15_4_ENABLE` from
`openthread-core-zephyr-config.h` which is now handled in
`modules/openthread/CMakeLists.tx`

Signed-off-by: Maciej Baczmanski <[email protected]>
(cherry picked from commit 3172748)

Author: maciejbaczmanski

modules/openthread/platform/openthread-core-zephyr-config.h

@@ -271,17 +271,6 @@
  */
 #define RADIO_CONFIG_SRC_MATCH_EXT_ENTRY_NUM 0
 
-/**
- * @def OPENTHREAD_CONFIG_RADIO_LINK_IEEE_802_15_4_ENABLE
- *
- * Set to 1 to enable support for IEEE802.15.4 radio link.
- *
- */
-#ifdef CONFIG_OPENTHREAD_RADIO_LINK_IEEE_802_15_4_ENABLE
-#define OPENTHREAD_CONFIG_RADIO_LINK_IEEE_802_15_4_ENABLE \
-	CONFIG_OPENTHREAD_RADIO_LINK_IEEE_802_15_4_ENABLE
-#endif /* CONFIG_OPENTHREAD_RADIO_LINK_IEEE_802_15_4_ENABLE */
-
 /**
  * @def OPENTHREAD_CONFIG_RADIO_LINK_TREL_ENABLE
  *