drivers: lkdtm: fix clang -Wformat warning

When building with Clang we encounter the following warning
(ARCH=hexagon + CONFIG_FRAME_WARN=0):
| ../drivers/misc/lkdtm/bugs.c:107:3: error: format specifies type
| 'unsigned long' but the argument has type 'int' [-Werror,-Wformat]
|                 REC_STACK_SIZE, recur_count);
|                 ^~~~~~~~~~~~~~

Cast REC_STACK_SIZE to `unsigned long` to match format specifier `%lu`
as well as maintain symmetry with `#define REC_STACK_SIZE
(_AC(CONFIG_FRAME_WARN, UL) / 2)`.

Link: ClangBuiltLinux#378
Fixes: 24cccab ("lkdtm/bugs: Adjust recursion test to avoid elision")
Reported-by: Nathan Chancellor <nathan@kernel.org>
Suggested-by: Nathan Chancellor <nathan@kernel.org>
Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Justin Stitt <justinstitt@google.com>
Link: https://lore.kernel.org/r/20220721215706.4153027-1-justinstitt@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: JustinStitt

drivers/misc/lkdtm/bugs.c

@@ -29,7 +29,7 @@ struct lkdtm_list {
 #if defined(CONFIG_FRAME_WARN) && (CONFIG_FRAME_WARN > 0)
 #define REC_STACK_SIZE (_AC(CONFIG_FRAME_WARN, UL) / 2)
 #else
-#define REC_STACK_SIZE (THREAD_SIZE / 8)
+#define REC_STACK_SIZE (THREAD_SIZE / 8UL)
 #endif
 #define REC_NUM_DEFAULT ((THREAD_SIZE / REC_STACK_SIZE) * 2)