bugs/core: Extend __WARN_FLAGS() with the 'cond_str' parameter

bugs/core: Extend __WARN_FLAGS() with the 'cond_str' parameter

Push the new parameter down into every architecture that defines __WARN_FLAGS():

  arm64
  loongarch
  parisc
  powerpc
  riscv
  s390
  sh
  x86

Don't pass anything substantial down yet, just propagate the
new parameter with empty strings, without generating it or
using it.

( The string is never NULL, so it can be concatenated at the
  preprocessor level. )

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/20250515124644.2958810-2-mingo@kernel.org