checkpatch: enable check for switch/case alignment

Now that the whole code is aligned with the coding style, enforce
the check through checkpatch.

Change-Id: Ie74ed98c5dfa61978d5551b60eb90acf746a3cc5
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/9057
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>
Tested-by: jenkins

.checkpatch.conf

@@ -23,6 +23,5 @@
 --ignore PREFER_KERNEL_TYPES
 --ignore SPLIT_STRING
 --ignore SSCANF_TO_KSTRTO
---ignore SWITCH_CASE_INDENT_LEVEL
 --ignore TRACING_LOGGING
 --ignore VOLATILE