EDAC, sb_edac: Fix signedness bugs in *_get_ha() functions

A static checker gave the following warnings:

  drivers/edac/sb_edac.c:1030 ibridge_get_ha() warn: signedness bug returning '(-22)'
  drivers/edac/sb_edac.c:1037 knl_get_ha() warn: signedness bug returning '(-22)'

Both because the functions are declared to return a "u8", but try to
return -EINVAL for the error case.

Fix by returning 0xff (since the caller doesn't look at, or pass on, the
return value).

Reported-by: Dan Carpenter <[email protected]>
Signed-off-by: Tony Luck <[email protected]>
Cc: Qiuxu Zhuo <[email protected]>
Cc: linux-edac <[email protected]>
Link: http://lkml.kernel.org/r/20180914201905.GA30946@agluck-desk
Signed-off-by: Borislav Petkov <[email protected]>

drivers/edac/sb_edac.c

@@ -1027,14 +1027,14 @@ static u8 ibridge_get_ha(u8 bank)
 	case 9 ... 16:
 		return (bank - 9) / 4;
 	default:
-		return -EINVAL;
+		return 0xff;
 	}
 }
 
 /* Not used, but included for safety/symmetry */
 static u8 knl_get_ha(u8 bank)
 {
-	return -EINVAL;
+	return 0xff;
 }
 
 static u64 haswell_get_tolm(struct sbridge_pvt *pvt)