ARCH OMAP : enable ARCH_HAS_HOLES_MEMORYMODEL for OMAP

OMAP platforms(like OMAP3530) include DSP or other co-processors
for media acceleration. when carving out memory for the
accelerators we can end up creating a hole in the memory map
of sort:
<kernel memory><hole(memory for accelerator)><kernel memory>

To handle such a memory configuration ARCH_HAS_HOLES_MEMORYMODEL
has to be enabled. For further information refer discussion at:
http://www.mail-archive.com/linux-omap@vger.kernel.org/msg15262.html.

Signed-off-by: Sriramakrishnan <srk@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>