ANDROID: configs: merge AOSP config fragments

Upstream now supports AOSP kernel config fragments:
commit 27eb6622 ("config: add android config fragments").

This patch merge non-upstream AOSP config fragments from
android/configs/android-* of common kernel experimental/android-4.9
to kernel/configs/android-*.

Added initial set of AOSP config fragments and a README.android,
from AOSP Change-ID: I3a4883f3b04d2820e90ceb3c4d02390d6458d6ce
("android: configs: Initial commit of Android config fragments"),
to explain the purpose of Android config fragments and how to use
them to generate a device config compatible with Android.

Signed-off-by: Amit Pundir <amit.pundir@linaro.org>