manuals: add references to the "do_rootfs" task

[YOCTO #14508]
Reported-by: Quentin Schulz <foss@0leil.net>
(From yocto-docs rev: 926c836e5184243fb1aee113962e11c01f0297ee)

Signed-off-by: Michael Opdenacker <michael.opdenacker@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/dev-manual/common-tasks.rst

@@ -3854,7 +3854,7 @@ to be added to the recipe that builds the ``core-image-sato`` image::
 
 In this example, the `from_multiconfig` is "x86". The `to_multiconfig` is "arm". The
 task on which the :ref:`ref-tasks-image` task in the recipe depends is the
-``do_rootfs`` task from the ``core-image-minimal`` recipe associated
+:ref:`ref-tasks-rootfs` task from the ``core-image-minimal`` recipe associated
 with the "arm" multiconfig.
 
 Once you set up this dependency, you can build the "x86" multiconfig
@@ -3864,7 +3864,7 @@ using a BitBake command as follows::
 
 This command executes all the tasks needed to create the
 ``core-image-sato`` image for the "x86" multiconfig. Because of the
-dependency, BitBake also executes through the ``do_rootfs`` task for the
+dependency, BitBake also executes through the :ref:`ref-tasks-rootfs` task for the
 "arm" multiconfig build.
 
 Having a recipe depend on the root filesystem of another build might not
@@ -9041,7 +9041,7 @@ Class methods are as follows:
 
 -  *hasPackage(pkg):* Returns "True" if ``pkg`` is in the installed
    package list of the image, which is based on the manifest file that
-   is generated during the ``do_rootfs`` task.
+   is generated during the :ref:`ref-tasks-rootfs` task.
 
 -  *hasFeature(feature):* Returns "True" if the feature is in
    :term:`IMAGE_FEATURES` or