libnvdimm, pfn: Fix over-trim in trim_pfn_device()

When trying to see whether current nd_region intersects with others,
trim_pfn_device() has already calculated the *size* to be expanded to
SECTION size.

Do not double append 'adjust' to 'size' when calculating whether the end
of a region collides with the next pmem region.

Fixes: ae86cbfe "libnvdimm, pfn: Pad pfn namespaces relative to other regions"
Cc: <stable@vger.kernel.org>
Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>