docs: x86: move two x86-specific files to x86 arch dir

Those two docs belong to the x86 architecture:

   Documentation/Intel-IOMMU.txt -> Documentation/x86/intel-iommu.rst
   Documentation/intel_txt.txt -> Documentation/x86/intel_txt.rst

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
diff --git a/MAINTAINERS b/MAINTAINERS
index 699596d9..f33487d 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -8312,7 +8312,7 @@
 W:	http://tboot.sourceforge.net
 T:	hg http://tboot.hg.sourceforge.net:8000/hgroot/tboot/tboot
 S:	Supported
-F:	Documentation/intel_txt.txt
+F:	Documentation/x86/intel_txt.rst
 F:	include/linux/tboot.h
 F:	arch/x86/kernel/tboot.c