mmc: sdhci-pltfm: use devm_ioremap_resource()

The chain of devm_request_mem_region() and devm_ioremap() can be
replaced with devm_ioremap_resource().  Also, we can drop the error
messages because devm_ioremap_resource() displays similar messages
on error.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>