defconfig: bengal: Disable ZONE_DMA32

The disabling of the ZONE_DMA32 is done to see if zone DMA
could be removed with the expectation that the disabling
of the DMA zone would facilitate faster physical memory
allocation.The removal of the dma zone opens up the
possibility to save memory by merging the lower reserved
memory with the normal zone. This config option can be
enabled, if any of the clients are not be able to
support due to hardware constraints.

Change-Id: I0377c23021f0f371d8cb0fdce37668bff3c51812
Signed-off-by: Prakash Gupta <guptap@codeaurora.org>