staging: comedi: comedi_isadma: fix "stalled" detect in comedi_isadma_disable_on_sample()

The "stalled" variable this function is used to detect if the DMA operation
is stalled while trying to disable DMA on a full comedi sample. The reset
of this variable should only occur when the remaining bytes of the DMA
transfer does not equal the remaining bytes from the last check.

Reported-by: coverity (CID 1271132)
Signed-off-by: NH Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: NIan Abbott <abbotti@mev.co.uk>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/drivers/comedi_isadma.c

@@ -91,9 +91,10 @@ unsigned int comedi_isadma_disable_on_sample(unsigned int dma_chan,
 			stalled++;
 			if (stalled > 10)
 				break;
+		} else {
+			residue = new_residue;
+			stalled = 0;
 		}
-		residue = new_residue;
-		stalled = 0;
 	}
 	return residue;
 }