mmc: sdhci-msm: factorise sdhci_msm_pdata outisde of sdhci_msm_host

There's no need to allocate one sdhci_msm_pdata for each sdhci_msm_host.
This patch removes the sdhci_msm_pdata member from sdhci_msm_host and
uses one static global sdhci_msm_pdata for all sdhci msm hosts. It also
marks sdhci_msm_ops as const.

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