ARM: mach-shmobile: Set CONSISTENT_DMA_SIZE to 158 MB

This patch sets CONSISTENT_DMA_SIZE to 158 MB
for all SH-Mobile ARM processors.

The DMA area is mapped at 0xf6000000 - 0xffdfffff,
on top of the 256 MB I/O window at 0xe6000000.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>