EDAC, pnd2: Fix Apollo Lake DIMM detection

Non-existent or empty DIMM slots result in error return from
RD_REGP(). But we shouldn't give up on failure.

So long as we find at least one DIMM we can continue.

Signed-off-by: Tony Luck <tony.luck@intel.com>
Cc: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
Link: http://lkml.kernel.org/r/20170628234407.21521-1-tony.luck@intel.com


Signed-off-by: Borislav Petkov <bp@suse.de>