clk: ux500: Drop .is_prepared state from PRCMU clocks

clk: ux500: Drop .is_prepared state from PRCMU clocks

The core already keeps a software prepare count. Drop this
custom software prepare count.

The only semantic difference is that if disabling the clock
fails, .is_prepared() will still return 1, but this will only
serve to confuse the framework, the error message is
sufficient.

Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20220414221751.323525-4-linus.walleij@linaro.org
Signed-off-by: Stephen Boyd <sboyd@kernel.org>