f2fs: Fix data corruption issue observed with FBE

There seems to be an integration mistake due to which
the dun is not getting set properly in the read path.
This results into data corruption issues when FBE/ICE
is enabled on F2FS.

Change-Id: I938e460ce1f8c297b6af918ada91ac2cf02fa342
Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>