drm/msm: handle gem bo flags during dma buffer mapping

This patch adds a new MSM_BO_KEEPATTRS flag on the internal
msm gem object structure and propagates it to the msm_gem
module's map_dma_buf callback. This allows gem objects to
be created that specify the DMA_ATTR_IOMMU_USE_UPSTREAM_HINT
attribute during buffer mappings.

CRs-Fixed: 2048692
Change-Id: I0f38fae9e5e83846a64f47f9c5b0954dbc11b4e4
Signed-off-by: Clarence Ip <cip@codeaurora.org>