fbdev: changes to enable recovery ui

In recovery UI path, fb_mmap is done to map the framebuffer
before iommu is attached. As this results in swio_tlb errors
leading to map failure, force a blank/unblank to make sure
iommu attach is done before calling dma_buf_map apis.

Change-Id: Ie90183273f119037acc521ef2eec2c8968c57920
Signed-off-by: Nirmal Abraham <nabrah@codeaurora.org>
Signed-off-by: Raghavendra Ambadas <rambad@codeaurora.org>