libpldm: Migrate to subproject

Organize files in libpldm to make it a subproject

In the current state, libpldm is not readily consumable
as a subproject.This commit does all the necessary re-organisation
of the source code to make it work as a subproject.

There are no .c/.h files changes in this commit, only meson
changes and re-organising the code structure.

Signed-off-by: Manojkiran Eda <manojkiran.eda@gmail.com>
Change-Id: I20a71c0c972b1fd81fb359d604433618799102c6
diff --git a/meson_options.txt b/meson_options.txt
new file mode 100644
index 0000000..0197fa9
--- /dev/null
+++ b/meson_options.txt
@@ -0,0 +1,3 @@
+option('tests', type: 'feature', description: 'Build tests', value: 'enabled')
+option('oem-ibm', type: 'feature', description: 'Enable IBM OEM PLDM', yield: true)
+option('requester-api', type: 'feature', description: 'Enable libpldm requester API', value: 'enabled')