doc: install pyocd using pip2

pyocd does not exist as a python 3 module, use pip2 to install it.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>

doc/getting_started/installation_linux.rst

@@ -73,6 +73,11 @@ Install additional packages required for development with Zephyr::
    cd ~/zephyr  # or to your directory where zephyr is cloned
    pip3 install --user -r scripts/requirements.txt
 
+If you require pyocd, an open source python2 library for programming and
+debugging ARM Cortex-M microcontrollers, use this command::
+
+   pip2 install --user -r scripts/py2-requirements.txt
+
 CMake version 3.8.2 or higher is required. Check what version you have using
 ``cmake --version``, and if its an older version, check the backports or
 install a more recent version manually. For example, to install version

doc/getting_started/installation_mac.rst

@@ -64,6 +64,11 @@ Install tools to build Zephyr binaries:
    cd ~/zephyr   # or to the folder where you cloned the zephyr repo
    pip3 install --user -r scripts/requirements.txt
 
+If you require pyocd, an open source python2 library for programming and
+debugging ARM Cortex-M microcontrollers, use this command::
+
+   pip2 install --user -r scripts/py2-requirements.txt
+
 Source :file:`zephyr-env.sh` wherever you have cloned the Zephyr Git repository:
 
 .. code-block:: console

doc/getting_started/installation_win.rst

@@ -88,6 +88,11 @@ packages from their respective websites.
       cd %userprofile%\zephyr
       pip install --user -r scripts/requirements.txt
 
+#. If you require pyocd, an open source python2 library for programming and
+   debugging ARM Cortex-M microcontrollers, use this command::
+
+      pip2 install --user -r scripts/py2-requirements.txt
+
 #. The build system should now be ready to work with any toolchain installed in
    your system. In the next step you'll find instructions for installing
    toolchains for building both x86 and ARM applications.

scripts/py2-requirements.txt

@@ -0,0 +1 @@
+pyocd

scripts/requirements.txt

@@ -7,7 +7,6 @@ junit2html
 PyYAML==3.12
 ply==3.10
 hub==2.0
-pyocd
 gitlint
 pyelftools==0.24
 pykwalify