Use Android.soong.mk to handle mixed Android.mk and Android.bp dirs

When building with soong Android.mk files are ignored in directories
that have Android.bp files.  Only parts of bionic have been converted to
Android.bp files, including some directories that have subdirectories
with Android.mk files.

Add Android.soong.mk files to include subdirectories to any directory
that has an Android.bp file but also has subdirectories with only
Android.mk files.

Change-Id: Ibd3c27d51c44f7a4b42dad0bc747e357b4ae34ca