mmc: sdhci: Wait for SDHCI_INT_DATA_END when transferring.

mmc: sdhci: Wait for SDHCI_INT_DATA_END when transferring.

sdhci_transfer_data() function transfers the blocks passed up to the
number of blocks defined in mmc_data, but returns immediately once all
the blocks are transferred, even if the loop exit condition is not met
(bit SDHCI_INT_DATA_END set in the STATUS word).

When doing multiple writes to mmc, returning right after the last block
is transferred can cause the write to fail when sending the
MMC_CMD_STOP_TRANSMISSION command right after the
MMC_CMD_WRITE_MULTIPLE_BLOCK command, leaving the mmc driver in an
unconsistent state until reboot. This error was observed in the rpi3
board.

This patch waits for the SDHCI_INT_DATA_END bit to be set even after
sending all the blocks.

Test: Reliably wrote 2GiB of data to mmc in a rpi3.

Signed-off-by: Alex Deymo <deymo@google.com>
Reviewed-by: Simon Glass <sjg@chromium.org>