mmc: sdhci_f_sdh30: Fix the size passed to sdhci_alloc_host

sdhci_alloc_host() takes priv_size rather than
sizeof(struct sdhci_host) + priv_size.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>