dt-bindings: clock: Add 12nm clock device tree bindings

Add mdss dsi pll 12nm clock enums. Cherry-picked from
'commit 1bc0f5d76d74 ("clk: qcom: mdss: add dsi phy 12nm clock")'.

Change-Id: Ib77a33a4a9ad88d5f705ab9a5ee4a922c27ae437
Signed-off-by: Althaf Neelanchirayil <aneelanc@codeaurora.org>
Signed-off-by: Nirmal Abraham <nabrah@codeaurora.org>