fix: fast wipe also last 1MB of the device

This fully erases GPT partition table.

Backported from v2 branch, for Sidero Metal.

Signed-off-by: Andrey Smirnov <andrey.smirnov@siderolabs.com>

blockdevice/blockdevice_linux.go

@@ -223,8 +223,19 @@ func (bd *BlockDevice) FastWipe() error {
 	}
 
 	_, err = bd.WipeRange(0, wipeLength)
+	if err != nil {
+		return err
+	}
 
-	return err
+	// wipe the last FastWipeRange bytes of the device as well
+	if size >= FastWipeRange*2 {
+		_, err = bd.WipeRange(size-FastWipeRange, FastWipeRange)
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
 }
 
 // WipeRange the blockdevice [start, start+length).