clk: mdss-dsi-pll: add support for auto PLL calculator for 20nm PHY

Add code to support DSI auto PLL calculator for 8994 platform
that uses 20nm physical layer. Update the PLL configuration
and DSI PHY regulator configurations to the recommended
settings.

Change-Id: Ia3d7042d537539491317f99d7bcc2c480f850216
Signed-off-by: Chandan Uddaraju <chandanu@codeaurora.org>