Currently, the ROM region is needlessly too large.

The on-chip SRAM region of the next SoC will start from 0x04000000,
and this will cause the region overlap.

Mapping 0x04000000 for the ROM is enough.

Change-Id: I85ce0bb1120ebff2e3bc7fd13dc0fd15dfff5ff6
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>