This patch considers no iommu support to kernel space mapping
of console framebuffer.

Without iommu, we get physical address instead of device address
after dma_alloc_attrs function is called. So we should consider
the case without iommu when it maps console framebuffer with
kernel space.

Changelog v2:
- calll vunmap function only with iommu support.
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>