tools headers: kcfi: rename missed CONFIG_CFI_CLANG

Commit 23ef9d43 ("kcfi: Rename CONFIG_CFI_CLANG to CONFIG_CFI")
missed one instance of CONFIG_CFI_CLANG. Rename it to match the original
kernel header. This addresses the following build warning:

  Warning: Kernel ABI header differences:
    diff -u tools/include/linux/cfi_types.h include/linux/cfi_types.h

Cc: Kees Cook <kees@kernel.org>
Fixes: a5ba183b ("Merge tag 'hardening-v6.18-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux"

)
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Link: https://lore.kernel.org/r/20251006225148.1636486-1-cmllamas@google.com


Signed-off-by: Kees Cook <kees@kernel.org>