staging/android: prepare sw_sync files for de-staging

remove file paths in the comments and add short description about each
file.

v2: remove file paths instead of just change them.

v3: improve header description as sugggested by Eric
Signed-off-by: NGustavo Padovan <gustavo.padovan@collabora.co.uk>
Reviewed-by: NEric Engestrom <eric.engestrom@imgtec.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/android/sw_sync.c

 /*
- * drivers/dma-buf/sw_sync.c
+ * Sync File validation framework
  *
  * Copyright (C) 2012 Google, Inc.
  *

drivers/staging/android/sync_debug.c

 /*
- * drivers/base/sync.c
+ * Sync File validation framework and debug information
  *
  * Copyright (C) 2012 Google, Inc.
  *

drivers/staging/android/sync_debug.h

 /*
- * include/linux/sync.h
+ * Sync File validation framework and debug infomation
  *
  * Copyright (C) 2012 Google, Inc.
  *