Update the documentation for SRCPV

The variable SRCPV is deprecated since 4.3. Instead of including SRCPV
in PV, including the sign "+" is enough for bitbake to add the source
control information to PKGV during the packaging phase.

Update the documentation for SRCPV and the places where it was used.
When instructions previously referred to SRCPV, replace by mentioning to
include "+" in the assignment.

In most examples, "+git" is added to PV as it is the most popular SCM.
Simply adding "+" is also possible, although it is better practice to
include the SCM name, so give that example.

Update the gcompat example with l3afpad as it didn't include "+git" in
its PV definition anymore.

(From yocto-docs rev: ee16c96202e5027d1a8d7e89e11c25f127c78326)

Signed-off-by: Antonin Godard <antonin.godard@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/dev-manual/packages.rst

@@ -84,10 +84,6 @@ the following:
 
 -  :term:`PR`: The recipe revision.
 
--  :term:`SRCPV`: The OpenEmbedded
-   build system uses this string to help define the value of :term:`PV` when
-   the source code revision needs to be included in it.
-
 -  :yocto_wiki:`PR Service </PR_Service>`: A
    network-based service that helps automate keeping package feeds
    compatible with existing package manager applications such as RPM,
@@ -256,15 +252,14 @@ the software::
 
    SRCREV = "${AUTOREV}"
 
-Furthermore, you need to reference :term:`SRCPV` in :term:`PV` in order to
+Furthermore, you need to include a ``+`` sign in :term:`PV` in order to
 automatically update the version whenever the revision of the source
 code changes. Here is an example::
 
-   PV = "1.0+git${SRCPV}"
+   PV = "1.0+git"
 
-The OpenEmbedded build system substitutes :term:`SRCPV` with the following:
-
-.. code-block:: none
+The OpenEmbedded build system will automatically add the source control
+information to the end of the variable :term:`PKGV`, in this format::
 
    AUTOINC+source_code_revision