mmc: sdhci: remove CONFIG_MMC_DEBUG from the driver

sdhci uses CONFIG_MMC_DEBUG for showing ADMA descriptor
when occurring ADMA error. And it's also used to  dump the
registers whenever calling sdhci_add_host.

On one hand, I don't see any burden to always print the state
ADMA descriptor as it's rare and will help folks better understand
what was happening when seeing ADMA error.

On the other, folks may be interested in checking some registers
at probe time. So we remove the sdhci_dumpregs from __sdhci_add_host
and print some really useful registers in sdhci_setup_host.

Suggested-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>