docs: kvm: Convert nested-vmx.txt to ReST format

This file is almost in ReST format. Just a small set of
changes were needed:

- Add markups for lists;
- Add markups for a literal block;
- Adjust whitespaces.

While here, use the standard markup for the document title.

Signed-off-by: Mauro Carvalho Chehab <[e-mail]>
Signed-off-by: Paolo Bonzini <[e-mail]>

Documentation/virt/kvm/index.rst

···
    locking
    mmu
    msr
+   nested-vmx
    vcpu-requests
 
    arm/index

Documentation/virt/kvm/nested-vmx.txt Documentation/virt/kvm/nested-vmx.rst

···
+.. SPDX-License-Identifier: GPL-2.0
+
+==========
 Nested VMX
 ==========
 
···
 emulated CPU type (qemu64) does not list the "VMX" CPU feature, so it must be
 explicitly enabled, by giving qemu one of the following options:
 
-     -cpu host              (emulated CPU has all features of the real CPU)
+     - cpu host              (emulated CPU has all features of the real CPU)
 
-     -cpu qemu64,+vmx       (add just the vmx feature to a named CPU type)
+     - cpu qemu64,+vmx       (add just the vmx feature to a named CPU type)
 
 
 ABIs
···
 of this structure changes, this can break live migration across KVM versions.
 VMCS12_REVISION (from vmx.c) should be changed if struct vmcs12 or its inner
 struct shadow_vmcs is ever changed.
+
+::
 
 	typedef u64 natural_width;
 	struct __packed vmcs12 {
···
 -------
 
 These patches were written by:
-     Abel Gordon, abelg <at> il.ibm.com
-     Nadav Har'El, nyh <at> il.ibm.com
-     Orit Wasserman, oritw <at> il.ibm.com
-     Ben-Ami Yassor, benami <at> il.ibm.com
-     Muli Ben-Yehuda, muli <at> il.ibm.com
+    - Abel Gordon, abelg <at> il.ibm.com
+    - Nadav Har'El, nyh <at> il.ibm.com
+    - Orit Wasserman, oritw <at> il.ibm.com
+    - Ben-Ami Yassor, benami <at> il.ibm.com
+    - Muli Ben-Yehuda, muli <at> il.ibm.com
 
 With contributions by:
-     Anthony Liguori, aliguori <at> us.ibm.com
-     Mike Day, mdday <at> us.ibm.com
-     Michael Factor, factor <at> il.ibm.com
-     Zvi Dubitzky, dubi <at> il.ibm.com
+    - Anthony Liguori, aliguori <at> us.ibm.com
+    - Mike Day, mdday <at> us.ibm.com
+    - Michael Factor, factor <at> il.ibm.com
+    - Zvi Dubitzky, dubi <at> il.ibm.com
 
 And valuable reviews by:
-     Avi Kivity, avi <at> redhat.com
-     Gleb Natapov, gleb <at> redhat.com
-     Marcelo Tosatti, mtosatti <at> redhat.com
-     Kevin Tian, kevin.tian <at> intel.com
-     and others.
+    - Avi Kivity, avi <at> redhat.com
+    - Gleb Natapov, gleb <at> redhat.com
+    - Marcelo Tosatti, mtosatti <at> redhat.com
+    - Kevin Tian, kevin.tian <at> intel.com
+    - and others.