mmc: sdhci-acpi: Add 64-bit DMA support

Set the DMA mask during the first call to ->enable_dma() to
make use of the SDHCI_USE_64_BIT_DMA flag.

This patch is dependent on
commit 8a2f38dd ("ACPI / platform: provide default DMA mask")
which provides the dev->dma_mask pointer without
which dma_set_mask_and_coherent() will always fail.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>