clk: ux500: Support prcmu ape opp voltage clock

Some scalable prcmu clocks needs to be handled in conjuction with the
ape opp 100 voltage. A new prcmu clock type clk_prcmu_opp_volt_scalable
is implemented to handle this.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Mike Turquette <mturquette@linaro.org>