clk: qcom: sm8150: define vdd_levels enum and vdd_corner[] map

Define a vdd_levels enum and vdd_corner[] mapping table which can
be used by clock controller drivers to configure the vdd_class
associated with their clocks.

Change-Id: Iae5551770c1bda12756464fa9d2f68ae571f87e9
Signed-off-by: Veera Vegivada <vvegivad@codeaurora.org>