mmc: sdhci-pltfm: remove priv variable from sdhci_pltfm_host

Now all clients migration to use sdhci_pltfm_init for private
allocation is done and there's no users of the priv variable, so we can
remove it from the sdhci_pltfm_host structure.

Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>