mmc: sdhci-msm: Factor out sdhci_msm_hs400

Factor out sdhci_msm_hs400 used for DLL calibration in HS400
modes. This function will be needed for enhanced_strobe as well.

Signed-off-by: Ritesh Harjani <riteshh@codeaurora.org>
Tested-by: Jeremy McNicoll <jeremymc@redhat.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>