Revert "msm: kgsl: Call dma_buf_unmap_attachment() early"

This reverts commit 0f09e6d0.

This patch is reported to be causing screen corruption issues
with camera and some display use cases, so reverting this change
until the root cause and fix is identified.

Change-Id: I13677a05f358b445eaaa62a927f9bef5e14e0613
Signed-off-by: Sharat Masetty <smasetty@codeaurora.org>