OMAP: TILER: Optimize placement for NV12 buffers

This patch changes the behaviour when allocating 2D buffers.  If
the required alignment is less than 4KiB and a security token is set,
the allocation will be flagged specifically for this format.  All
subsequent buffers of the same format and size will be placed inside
this area until the area is exhausted.

For NV12 allocations, this means that all Y allocations will share
one area, and the UV allocations will share another.

Change-Id: I13d29257c0cbab627c2938d4623557918448ee86
Signed-off-by: Andy Gross <andy.gross@ti.com>
TILER: Add tiler_backpages method

tiler_backpages method can be used to get the number of pages
required for a tiler allocation.  This method is called before
the memory is partitioned, therefore, we cannot rely on tiler
being initialized.  Separated geometry initialization for this
purpose.

Change-Id: Ia68cbd81c31a357fdc51036753db222d21994996
Signed-off-by: Lajos Molnar <lajos@ti.com>
Signed-off-by: Dima Svetlov <svetlov@ti.com>