mfd: qcom,tcsr: Add device tree binding for TCSR

This patch adds the device tree binding for the Qualcomm Top Control and
Status Register device.  The TCSR is comprised of a set of registers that
provide various control and status functions for attached peripherals.

Signed-off-by: Andy Gross <agross@codeaurora.org>
Signed-off-by: Kumar Gala <galak@codeaurora.org>
Signed-off-by: Olof Johansson <olof@lixom.net>