dt-bindings: clock: Add mdss-28nm-pll-clk for legacy targets

Create new header copied from mdss-28nm-pll-clk.h and rename
enums for legacy targets.

Change-Id: I5426369d05346fdf13021b21e239ffe0d43c4436
Signed-off-by: Nirmal Abraham <nabrah@codeaurora.org>