Revert "r[moto] clock: remove dsi1 escape clock source setting"

This reverts commit 5a6609eda7b9665a648039f5899503bb9bba93c9.
board-mmi-common: Prepare iface_clk before enable

Fixes unwind:
gsbi4_p_clk: Never called prepare or calling disable after unprepare

Change-Id: Ifc8f02cf984a1956008aa3a4f1989d958e521c0a