fs_config: drop fs_config_files/dirs PRODUCT_PACKAGES requirement

When configuring fs_config_files or fs_config_dirs for file_system
capabilities, drop the requirement that OEMs must add the target
to PRODUCT_PACKAGES. This limits the configuration requirement
to only needing to set the new and preferred TARGET_FS_CONFIG_GEN
or the older TARGET_ANDROID_FILESYSTEM_CONFIG_H method.

Test: That only setting TARGET_FS_CONFIG_GEN results in passwd and
group in the build image.
Change-Id: I818854fa1b3e94edaff59a32bd7cf23cf9b504aa
Signed-off-by: William Roberts <william.c.roberts@intel.com>
diff --git a/tools/fs_config/README b/tools/fs_config/README
index b1507a7..c50c056 100644
--- a/tools/fs_config/README
+++ b/tools/fs_config/README
@@ -50,12 +50,12 @@
   prefixed with a 0, else mode is used as is.
 
 user:
-  The exact, C define for a valid AID. Note custom AIDs can be defined in the
+  Either the C define for a valid AID or the friendly name. For instance both
+  AID_RADIO and radio are acceptable. Note custom AIDs can be defined in the
   AID section documented below.
 
 group:
-  The exact, C define for a valid AID. Note custom AIDs can be defined in the
-  AID section documented below.
+  Same as user.
 
 caps:
   The name as declared in