GKI: samsung: drm: update dma_buf_vunmap

Commit 20e76f1a7059 ("dma-buf: Use struct dma_buf_map in
dma_buf_vunmap() interfaces") updates dma_buf_vunmap to use the
dma_buf_map pointer instead of the vaddr. So update the driver
accordingly.

Signed-off-by: Will McVicker <willmcvicker@google.com>
Change-Id: I8826af32cc25652806a1d556ed9c2bcbe8030149