clk: qcom: Add clk_ops to support runtime frequencies for esc clock

Some of the display panels requires multiple clock frequencies
to be derived runtime from the sources for its operation.
Add support for the same by adding esc clk_ops to calculate
the desired frequency at run time.

Change-Id: Ie3ec84bb1927f5313c887344368dceffb06035be
Signed-off-by: Taniya Das <tdas@codeaurora.org>