pinctrl: sunxi: Use of_clk_get_parent_count() instead of open coding

A new open coder has crept in since 470b73a3 ("pinctrl: sunxi:
Use of_clk_get_parent_count() instead of open coding"), replace it.

of_clk_get_parent_count() was moved to <linux/of_clk.h>, so include that
instead of <linux/clk-provider.h>.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>