Reserve 129th region in the memblock, and this will trigger the
memblock_double_array() function, this needs valid memory regions. So
using dummy_physical_memory_init() to allocate a valid memory region.
At the same time, reserve 128 faked memory region, and make sure these
reserved region not intersect with the valid memory region. So
memblock_double_array() will choose the valid memory region, and it will
success.

Also need to restore the reserved.regions after memblock_double_array(),
to make sure the subsequent tests can run as normal.
Signed-off-by: Shaoqin Huang <shaoqin.huang@intel.com>
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Link: https://lore.kernel.org/r/20221011062128.49359-3-shaoqin.huang@intel.com