msm: mdss: add support for multiple DSI host escape clk frequencies

Some panels have low escape clock requirements based on which the
host escape clock should be configured. Add support to configure
host escape clock based on the panel escape clock. By default, the
host would be configured for an escape clock of 19.2MHz.

Change-Id: If791ffb4d49dd97424366042ee35bd4ecda5c185
Signed-off-by: Ashish Garg <ashigarg@codeaurora.org>