sd/sdhci:ADMA: fix interrupt

The end of transfer check was occurring and potentially returning before
the interrupt flag was checked. This means the interrupt will be missed
if it occurs on the last packet. Fix by checking for the interrupt
before checking for the end of transfer.

Signed-off-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Reviewed-by: Igor Mitsyanko <i.mitsyanko@gmail.com>
Message-id: 9969ec154777957ec738fc4e539d68e7494d0081.1369370934.git.peter.crosthwaite@xilinx.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
