mmc: mmc: Move mmc_switch_status()

Move the mmc_switch_status() function in preparation for calling it
in mmc_select_hs400().

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: <stable@vger.kernel.org> # 4.2+
Tested-by: Alim Akhtar <alim.akhtar@samsung.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>