mmc: Use logging instead of printf()

mmc: Use logging instead of printf()

The code makes quite a few uses of __func__ which puts the function
name into the resulting SPL image. Use the log subsystem instead, to
reduce size.

The CONFIG_LOGF_FUNC option can be used to enable the function name.

Use lower-case hex for the status output in sdhci_transfer_data(), to
match sdhci_send_command()

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>