drivers/video: fsl-diu-fb: merge all allocated data into one block

The Freescale DIU driver allocates multiple blocks of memory, including
multiple DMA buffers.  Merge all of these blocks into one data structure.

Specifically:

1) struct fsl_diu_data now contains everything that needs to be allocated,
except for the framebuffers themselves.  DMA'able objects are aligned correctly
within the structure.

2) struct diu_addr is no longer needed, because we don't have to manage
multiple blocks of DMA memory.

3) Since there's no diu_addr any more, macro DMA_ADDR is used to calculate
the DMA address of any field in fsl_diu_data.

4) Functions allocate_buf() and free_buf() are no longer needed, because we
now assume that dma_alloc_coherent() will allocate a page-aligned block,
and everything is properly aligned with fsl_diu_data already, so we no longer
need to align any memory blocks ourselves.

5) The "dummy" area descriptor is now defined separately from the other
five ADs, so NUM_AOIS (previously called FSL_AOI_NUM) is now set to five
instead of six.  Previously, all six were combined together to avoid a
separate call to allocate_buf() just for the dummy AD.

6) framebuffer_alloc() and framebuffer_release() are no longer used.  The
framebuffer is initialized manually.

7) Error handling is simplified since there's only one memory buffer
allocated.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>