vboot/fastboot: Use common path for booting the kernel image

Use common path for booting the kernel image once its loaded in memory
either using VbSelectAndLoadKernel or using fastboot boot. This
ensures that the code for command line adjustments and device tree
modifications is not repeated everywhere.

BUG=None
BRANCH=None
TEST=Compiles successfully and boots to kernel prompt from disk as
well as fastboot boot.

Change-Id: Ic3f09d549050c29a7dfc32fd89670328d0c00380
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://chromium-review.googlesource.com/274132
Trybot-Ready: Furquan Shaikh <furquan@chromium.org>
Tested-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>
Commit-Queue: Furquan Shaikh <furquan@chromium.org>
3 files changed