README: update urls

Point at the git repositories on gitlab.arm.com.
Signed-off-by: Vincent Stehlé <vincent.stehle@arm.com>

README.rst

@@ -22,7 +22,7 @@ and run the repo init command::
 
   $ mkdir firmware-working
   $ cd firmware-working
-  $ repo init -u https://github.com/glikely/u-boot-manifest
+  $ repo init -u https://gitlab.arm.com/systemready/firmware-build/u-boot-manifest
   $ repo sync
 
 This will clone all of the required git trees and link the Makefile
@@ -54,4 +54,4 @@ More to come as this tool matures.
 3. QEMU aarch64 ``qemu_arm64_defconfig``
 4. Solidrun LX2k lx2160a-cex7 ``lx2160acex7_tfa_defconfig``
    Need to use git repos listed in ``lx2160a.xml``.
-   (see https://github.com/glikely/u-boot-manifest)
+   (see https://gitlab.arm.com/systemready/firmware-build/u-boot-manifest)