docs: fix broken documentation links

Mostly due to x86 and acpi conversion, several documentation
links are still pointing to the old file. Fix them.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Reviewed-by: Wolfram Sang <wsa@the-dreams.de>
Reviewed-by: Sven Van Asbroeck <TheSven73@gmail.com>
Reviewed-by: Bhupesh Sharma <bhsharma@redhat.com>
Acked-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
diff --git a/security/Kconfig b/security/Kconfig
index aeac367..6d75ed7 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -62,7 +62,7 @@
 	  ensuring that the majority of kernel addresses are not mapped
 	  into userspace.
 
-	  See Documentation/x86/pti.txt for more details.
+	  See Documentation/x86/pti.rst for more details.
 
 config SECURITY_INFINIBAND
 	bool "Infiniband Security Hooks"