msm: npu: Don't sync dma buffer after mapping

User driver will take care of flushing or invalidating dma buffer.
It's not needed to do it in kernel driver after mapping.

Change-Id: I8c3858bd84a5b74bd57cb67b91c4541b023a8d37
Signed-off-by: Jilai Wang <jilaiw@codeaurora.org>