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/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index f730680d..59f5985 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -156,7 +156,7 @@
 	  code. When you use it make sure you have a big enough
 	  IOMMU/AGP aperture.  Most of the options enabled by this can
 	  be set more finegrained using the iommu= command line
-	  options. See Documentation/x86/x86_64/boot-options.txt for more
+	  options. See Documentation/x86/x86_64/boot-options.rst for more
 	  details.
 
 config IOMMU_LEAK