README: use 'https://' instead of 'git://'

When you clone the repository without previous commit history, 'git://'
doesn't protect from man-in-the-middle attacks.  HTTPS is more secure
since the client verifies the server certificate.

Reported-by: Jann Horn <jannh@google.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Message-id: 2018110811.30671-2-stefanha@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

README

@@ -54,7 +54,7 @@ Submitting patches
 
 The QEMU source code is maintained under the GIT version control system.
 
-   git clone git://git.qemu.org/qemu.git
+   git clone https://git.qemu.org/git/qemu.git
 
 When submitting patches, one common approach is to use 'git
 format-patch' and/or 'git send-email' to format & send the mail to the
@@ -70,7 +70,7 @@ the QEMU website
 
 The QEMU website is also maintained under source control.
 
-  git clone git://git.qemu.org/qemu-web.git
+  git clone https://git.qemu.org/git/qemu-web.git
   https://www.qemu.org/2017/02/04/the-new-qemu-website-is-up/
 
 A 'git-publish' utility was created to make above process less

pc-bios/README

@@ -23,7 +23,7 @@
   legacy x86 software to communicate with an attached serial console as
   if a video card were attached.  The master sources reside in a subversion
   repository at http://sgabios.googlecode.com/svn/trunk.  A git mirror is
-  available at git://git.qemu.org/sgabios.git.
+  available at https://git.qemu.org/git/sgabios.git.
 
 - The PXE roms come from the iPXE project. Built with BANNER_TIME 0.
   Sources available at http://ipxe.org.  Vendor:Device ID -> ROM mapping:
@@ -40,7 +40,7 @@
 
 - The u-boot binary for e500 comes from the upstream denx u-boot project where
   it was compiled using the qemu-ppce500 target.
-  A git mirror is available at: git://git.qemu.org/u-boot.git
+  A git mirror is available at: https://git.qemu.org/git/u-boot.git
   The hash used to compile the current version is: 2072e72
 
 - Skiboot (https://github.com/open-power/skiboot/) is an OPAL