mmc: sdhci-pltfm: call platform_get_irq() before sdhci_alloc_host()

Swap the call order of sdhci_alloc_host() and platform_get_irq().
It makes sdhci_alloc_host() the last function that can fail in the
sdhci_pltfm_init().  So, we can drop the sdhci_free_host() call from
the failure path.

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>