tests: mem_map: limit memory below 0x10000000 on up_squared.

there is a memory hole from address 0x10000000-0x12150fff
in the ram on up_squared, we don't have access to read/write
this range, so limit the memory range below 0x10000000.

Signed-off-by: Chen Peng1 <peng1.chen@intel.com>