writeback: Drop I_DIRTY_TIME_EXPIRE

The only use of I_DIRTY_TIME_EXPIRE is to detect in
__writeback_single_inode() that inode got there because flush worker
decided it's time to writeback the dirty inode time stamps (either
because we are syncing or because of age). However we can detect this
directly in __writeback_single_inode() and there's no need for the
strange propagation with I_DIRTY_TIME_EXPIRE flag.

Change-Id: I8686cce5233666daf882f8c35edadd05c3b898e7
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Git-commit: 59e9f791
Git-repo: https://android.googlesource.com/kernel/common/


Signed-off-by: Pradeep P V K <ppvk@codeaurora.org>