cxl/mem: Adjust ram/pmem range to represent DPA ranges

cxl/mem: Adjust ram/pmem range to represent DPA ranges

CXL spec defines the volatile DPA range to be 0 to Volatile memory size.
It further defines the persistent DPA range to follow directly after the
end of the Volatile DPA through the persistent memory size.  Essentially

Volatile DPA range   = [0, Volatile size)
Persistent DPA range = [Volatile size, Volatile size + Persistent size)

Adjust the pmem_range start to reflect this and remote the TODO.

Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/20210617221620.1904031-4-ira.weiny@intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>