mmc: tmio: always unmap DMA before waiting for interrupt

In the (maybe academical) case, we don't get a DATAEND interrupt after
DMA completed, we will wait endlessly for the completion to complete.
This is not bad per se, since we have a more generic completion tracking
a timeout. In that rare case, however, the DMA buffer will not get
unmapped and we have a leak. Reorder the code, so unmapping will always
take place.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>