mmc: sdhci-msm: Factor out sdhci_msm_hc_select_mode

This factors out sdhci_msm_hc_select_mode to later use
it during enhanced_strobe mode select.
It also further breaks sdhci_msm_hc_select_mode
into separate functions for configuring HS400 mode
or other modes.

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>