ARM: dts: sony-rhine: Define boost regulator and correct sdhci node

With the boost regulator defined and the proper supply chain from l20 we
can call regulator_set_optimum_mode() on vmmc and with that run sdhci at
full speed.

Signed-off-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>
ARM: dts: sony-rhine: Specify vmmc and vqmmc load

Signed-off-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>