tools/wltests: add support for Pixel2 (wahoo)

This is a set of script to run wltests on a Pixel 2 device.
The main difference here wrt Hikey960 devices, is that kernel's modules
need to be pused to the device while still in ADB mode, before rebooting
into FASTBOOT to update the kernel.

A common flow to test on Pixel 2 devices is:

- build a tag release of AOSP to get the base images to flash the
  device. For example, android-8.1.0_r4 is the tag use to test this
  integartion.

- flash and boot the device with AOSP stock images

- configure the device for wltest:
  a) setup networking access
  b) install APKs required by wltests:
     https://github.com/ARM-software/lisa/blob/master/tools/wltests/agendas/sched-evaluation-full.yaml
  c) disable verity to allows / to be remounted RW:
     adb disable-verity
  d) reboot your device and ensure "adb remount" does not fails

- check which msm-gooogle kernel:
     https://android.googlesource.com/kernel/msm.git


  has been used to build the stock images by getting its SHA1 from:
     adb shell uname -a

  In the example above, if the previous command should return:
     Linux localhost 4.4.88-g4e9c66de2183-00019-gb04af4eb2ed4 ...
  then the base kernel is: b04af4eb2ed4

- rebase your patches on top if the base kernel's SHA1

This should give you a usable and working setup to experiment with Pixel
2 devices.

In order to build a Pixel kernel and all the related images, some binary
tools are also required which are available in a standard AOSP
installation. Thus, if you have a locally installed Android source tree,
let assume under AOSP_HOME, here is a suitable configuration for your
shell environment:

   # Your AOSP local installation
   export AOSP_HOME=/path/to/your/local/AOSP

   # Android SDK (for ADB and FASTBOOT)
   export ANDROID_HOME=/data/Android/android-sdk-linux

   # AOSP Prebuilts (gor GCC and DTC and other tools)
   export ANDROID_PREBUILTS=$AOSP_HOME/prebuilts
   export PATH_GCC=$ANDROID_PREBUILTS/gcc/linux-x86/aarch64/aarch64-linux-android-4.9/bin
   export PATH_DTC=$ANDROID_PREBUILTS/misc/linux-x86/dtc
   export PATH_MKI=$ANDROID_PREBUILTS/misc/linux-x86/libufdt
   export PATH_LZ4=$ANDROID_PREBUILTS/misc/linux-x86/lz4
   export PATH=$PATH_GCC:$PATH_DTC:$PATH_MKI:$PATH_LZ4:$PATH

   # Cross compiler setup
   export CROSS_COMPILE=aarch64-linux-android-
   export ARCH=arm64

With this setup in your environment, you'll be ready to run wltests on a
Pixel device using a command like, for example:

   lisa-wltest-series \
      --platform wahoo_android_v4.4 \
      --kernel_src /path/to/your/wahoo/kernel \
      --series /path/to/your/sha1.series \
      --wa_agenda tools/wltests/agendas/sched-evaluation-full.yaml \
      --results results/wltests_your_experiment_name \
      --acme_channels "1 2" \
      --device HT7821A00605 --force

Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com>
Suggested-by: Chris Redpath <chris.redpath@arm.com>