x86/cpu: Remove misleading comment

The comment of the "#endif" after setup_disable_pku() is wrong.

As the related #ifdef is only a few lines above, just remove the
comment.

Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230113130126.1966-1-jgross@suse.com