kbuild: Convert this project to an external module

This patch converts this project to an external modules. Here are the
steps taken:

1) Rename all Makefiles to Kbuild:

  find . -name Makefile | xargs -n1 bash -c 'mv "$0" `dirname "$0"`/Kbuild'

2) Create a base Makefile with the targets: modules, modules_install,
   and clean.

3) Update all the Kconfig files to use KCONFIG_EXT_PREFIX which is
   a relative path from the KERNEL_SRC. This allows us to use
   slider_gki.fragment to define which drivers to compile. We also need
   to rename the base Kconfig to Kconfig.ext.

4) Add the following new properties to the BUILD_CONFIG file in order to
   compile the DT out-of-tree and include Kconfig support for this
   project:

  KCONFIG_EXT_PREFIX=/path/to/this/repo
  DTS_EXT_DIR=/path/to/this/repo/arch/arm64/boot/dts
  DTC_INCLUDE=/path/to/this/repo/scripts/dtc/include-prefixes

5) Update paths in the BUILD_CONFIG file to reflect this projects new
   path.

6) Drop CONFIG_DEVICE_MODULES since we don't need it anymore.

We also need to update the other external modules to be able to find the
necessary includes in this project as well as be able to link to the
symbols defined in this project. To handle this, we can create the file
Makefile.include that defines the necessary EXTRA_CFLAGS and
EXTRA_SYMBOLS variables which then can be included in the Makefile of
all the external modules that need to #include headers from this project
or link to the modules compile by this project.

Bug: 206700303
Signed-off-by: Will McVicker <willmcvicker@google.com>
Change-Id: I2442032d1dcf6179dbf665418f4c7613e882c867

1 files changed, 0 insertions, 0 deletions

diff --git a/drivers/trusty/Makefile b/drivers/trusty/Kbuild
index 2cf1cfc..2cf1cfc 100644
--- a/drivers/trusty/Makefile
+++ b/drivers/trusty/Kbuild