msm: clock-8226: Remove vdd_class from kpss_ahb_clk

Since this clock may be enabled by other masters, Apps cannot be
responsible for voting for the proper voltage for this clock. Apps also
cannot leave a voltage vote for this clock all the time, as this prevents
setting voltage to retention levels.

Change-Id: Ia448e7d966950ff75639d97288f9ad725c96d945
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>