x86/cfi: Only define poison_cfi() if CONFIG_X86_KERNEL_IBT=y
poison_cfi() was introduced in:
9831c6253ace ("x86/cfi: Extend ENDBR sealing to kCFI")
... but it's only ever used under CONFIG_X86_KERNEL_IBT=y,
and if that option is disabled, we get:
arch/x86/kernel/alternative.c:1243:13: error: ‘poison_cfi’ defined but not used [-Werror=unused-function]
Guard the definition with CONFIG_X86_KERNEL_IBT.
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>