bugs/s390: Remove private WARN_ON() implementation

Besides an odd __builtin_constant_p() optimization the s390 specific
WARN_ON() implementation is identical to the generic variant.
Drop the s390 variant in favor of the generic variant.

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org> # Rebased ancestor commits
Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Link: https://lore.kernel.org/r/20250617135042.1878068-2-hca@linux.ibm.com

Author: hcahca

arch/s390/include/asm/bug.h

@@ -50,20 +50,7 @@ do {								\
 	unreachable();						\
 } while (0)
 
-#define WARN_ON(x) ({					\
-	int __ret_warn_on = !!(x);			\
-	if (__builtin_constant_p(__ret_warn_on)) {	\
-		if (__ret_warn_on)			\
-			__WARN();			\
-	} else {					\
-		if (unlikely(__ret_warn_on))		\
-			__WARN();			\
-	}						\
-	unlikely(__ret_warn_on);			\
-})
-
 #define HAVE_ARCH_BUG
-#define HAVE_ARCH_WARN_ON
 
 #include <asm-generic/bug.h>