CHROMIUM: rockchip: support prime import sg table

CHROMIUM: rockchip: support prime import sg table

The prime fd to handle ioctl was not used with rockchip before. Support
was added in order to pass graphics_Gbm and to support potential uses
within Chrome OS (e.g. zero-copy video decode, camera).

Difference from kernel 3.14 implementation:
- prime_import_sg_table passes dma-buf as argument instead of size
- need to handle import sg_table for both DMA and IOMMU paths

TEST=test_that graphics_Gbm on kevin
BUG=chrome-os-partner:56526

Reviewed-on: https://chromium-review.googlesource.com/381991
Tested-by: Haixia Shi <hshi@chromium.org>
Commit-Queue: Haixia Shi <hshi@chromium.org>
Trybot-Ready: Haixia Shi <hshi@chromium.org>
Reviewed-by: Haixia Shi <hshi@chromium.org>
Reviewed-by: Stéphane Marchesin <marcheu@chromium.org>
Conflicts:
	drivers/gpu/drm/rockchip/rockchip_drm_gem.c

Change-Id: I7aae5b0e227de61ac17adf98996152da8db097d2
Signed-off-by: Randy Li <randy.li@rock-chips.com>