msm: ipaut: Do not use kernel file object after write fop returns

file* object passed via write fop cannot be used after
write returns as it may be freed. Any needed data, need
to be saved before write returns.

CRs-fixed: 2174721
Change-Id: I69473c7000b193b6353efdb21d1f4c98dcdc5e8c
Signed-off-by: Ghanim Fodi <gfodi@codeaurora.org>