mmc: mvsdio: Fix dma_unmap_sg() nents value

commit 8ab2f1c35669bff7d7ed1bb16bf5cc989b3e2e17 upstream.

The dma_unmap_sg() functions should be called with the same nents as the
dma_map_sg(), not the value the map function returned.

Fixes: 236caa7c ("mmc: SDIO driver for Marvell SoCs")
Signed-off-by: Thomas Fourier <fourier.thomas@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Cc: stable@vger.kernel.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>