soc: neorv32: stop pretending to support multiple versions

Originally, when Zephyr support for the NEORV32 was introduced, the idea
was to support multiple version of the SoC in Zephyr as development on the
open-source RISC-V processor continued.

Unfortunately, this has proven to be much harder than anticipated in part
due to incompatible changes between NEORV32 versions and part due to the
added test burden of verifying all changes on many different versions and
configurations.

Going forward, Zephyr will support a given release of the NEORV32
processor.

Signed-off-by: Henrik Brix Andersen <henrik@brixandersen.dk>

boards/others/neorv32/Kconfig

@@ -1,5 +0,0 @@
-# Copyright (c) 2021 Henrik Brix Andersen <henrik@brixandersen.dk>
-# SPDX-License-Identifier: Apache-2.0
-
-config BOARD_NEORV32
-	select SOC_NEORV32_V1_8_6 if "$(BOARD_REVISION)" = "1.8.6"

boards/others/neorv32/board.yml

@@ -2,10 +2,5 @@ board:
   name: neorv32
   full_name: NEORV32
   vendor: others
-  revision:
-    format: major.minor.patch
-    default: "1.8.6"
-    revisions:
-      - name: "1.8.6"
   socs:
     - name: neorv32

soc/neorv32/Kconfig

@@ -15,12 +15,9 @@ config SOC_NEORV32
 
 if SOC_NEORV32
 
-config SOC_NEORV32_V1_8_6
-	bool "v1.8.6"
-
 config SOC_NEORV32_VERSION
 	hex
-	default 0x01080600 if SOC_NEORV32_V1_8_6
+	default 0x01080600
 	help
 	  The targeted NEORV32 version as BCD-coded number. The format is
 	  identical to that of the NEORV32 Machine implementation ID (mimpid)