bugs/core: Pass down the condition string of WARN_ON_ONCE(cond) warnings to __WARN_FLAGS()

Doing this will allow architecture code to store and print out
this information as part of the WARN_ON and BUG_ON facilities.

The format of the string is '[condition]', for example:

  WARN_ON_ONCE(idx < 0 && ptr);

Will get the '[idx < 0 && ptr]' string literal passed down as 'cond_str'
in __WARN_FLAGS().

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-arch@vger.kernel.org
Link: https://lore.kernel.org/r/20250515124644.2958810-3-mingo@kernel.org

include/asm-generic/bug.h

@@ -110,7 +110,7 @@ extern __printf(1, 2) void __warn_printk(const char *fmt, ...);
 #define WARN_ON_ONCE(condition) ({				\
 	int __ret_warn_on = !!(condition);			\
 	if (unlikely(__ret_warn_on))				\
-		__WARN_FLAGS("",				\
+		__WARN_FLAGS("["#condition"] ",			\
 			     BUGFLAG_ONCE |			\
 			     BUGFLAG_TAINT(TAINT_WARN));	\
 	unlikely(__ret_warn_on);				\