clk/qcom/mdss: add DSI 7nm PLL support

This change adds support for DSI 7nm PLL configuration.
This change also registers the list of clocks, those are
possible to be sourced from 7nm PLL, with clock driver.

Change-Id: Ib6a95983e519b8e22208381ce0f7938fa4b0aeae
Signed-off-by: Govinda Rajulu Chenna <gchenna@codeaurora.org>