rasdaemon: make sure the error is valid before handling ranks

rasdaemon: make sure the error is valid before handling ranks

Fix "rank" handling according to the Bit 63 description in Intel SDM Vol.3C
Table 16-23, that says "... Use this information only after there is valid
first error info indicated by bit 62".
Also fix invalid comparisons of unsigned variables "rank0" and "rank1".

Signed-off-by: Seiichi Ikarashi <s.ikarashi@jp.fujitsu.com>
Signed-off-by: Aristeu Rozanski <aris@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>