mmc: sdhci-of-arasan: Omit superfluous error messages

sdhci_add_host and sdhci_platfm_init already report failure,
so don't emit error messages when a failure occurs. This prevents
occurences of "deferred" messages when required power supplies
are not ready for operation yet.

Signed-off-by: Mike Looijmans <mike.looijmans@topic.nl>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>