clk: clk-gpio: Request GPIO descriptor as LOW

Requesting the GPIOD_OUT_LOW low will make sure the GPIO is
deasserted when requested. The gpiolib core will make sure that
if the GPIO line is active low, it will be logically driven high
when deasserted, see drivers/gpiolib.c gpiod_configure_flags().

Cc: Sergej Sawazki <ce3a@gmx.de>
Cc: Jyri Sarha <jsarha@ti.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>