lib: at_parser: move generated code and ignore formatting

Moves the generated `at_match.c` to the `generated` directory
and adds this directory to the excluded list for Checkpatch,
so that the generated file does not require reformatting.
This makes versioning easier since it removes the reformatting
step necessary to comply with Checkpatch.

Signed-off-by: Mirko Covizzi <mirko.covizzi@nordicsemi.no>

.checkpatch.conf

@@ -49,4 +49,5 @@
 --exclude doc/nrf/.*/.*/.*/images
 --exclude doc/nrf/.*/.*/.*/.*/images
 --exclude applications/nrf5340_audio/src/utils/macros
+--exclude lib/at_parser/generated
 --exclude lib/bin/lwm2m_carrier/include

lib/at_parser/CMakeLists.txt

@@ -7,7 +7,7 @@
 zephyr_library()
 zephyr_library_sources(
 	at_parser.c
-	at_match.c
+	generated/at_match.c
 )
 
 zephyr_include_directories(include)

lib/at_parser/at_match.re

@@ -4,19 +4,14 @@
  * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
  */
 
-/* at_match.c generated by re2c 3.0
+/* at_match.c generated by re2c 3.0-1
  *
  * Generated with:
- *   re2c at_match.re -o at_match.c -W --no-debug-info --tags
- *
- * Reformatted with:
- *   clang-format-15 -i at_match.c
- * Using the following additional .clangformat options:
- *   IndentGotoLabels: false
- *   SpaceBeforeInheritanceColon: False
+ *   re2c at_match.re -o generated/at_match.c -W --tags --no-debug-info --no-generation-date \
+ *   	--no-version
  */
 
-#include "at_match.h"
+#include "../at_match.h"
 
 struct at_token at_match_cmd(const char *at, const char **remainder)
 {