[SCSI] Unify SAM_ and SAM_STAT_ macros

We have two separate definitions for identical constants with nearly the
same name.  One comes from the generic headers in scsi.h; the other is
an enum in libsas.h ... it's causing confusion about which one is
correct (fortunately they both are).

Fix this by eliminating the libsas.h duplicate

Signed-off-by: James Bottomley <James.Bottomley@suse.de>