sdhci: attach fixed regulator to sdhci host controller.

sdhci: attach fixed regulator to sdhci host controller.

BZ: 15061

The WIFI requires a fixed regulator to enable / disable the chip.
So in the early device initialization, the regulator shall be requested
for the sdhci host controller.

Change-Id: I1e2b779c85f7cf14e2d24a3ed1bc651e8b0c8805
Signed-off-by: Aymen Zayet <aymenx.zayet@intel.com>
Reviewed-on: http://android.intel.com:8080/25381
Reviewed-by: Champciaux, NicolasX <nicolasx.champciaux@intel.com>
Tested-by: Champciaux, NicolasX <nicolasx.champciaux@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>