pinctrl: samsung: fix leaked of_node references

The call to of_find_compatible_node returns a node pointer with refcount
incremented thus it must be explicitly decremented after the last
usage.

Detected by coccinelle with the following warnings:
./drivers/pinctrl/samsung/pinctrl-exynos-arm.c:76:2-8: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 66, but without a corresponding object release within this function.
./drivers/pinctrl/samsung/pinctrl-exynos-arm.c:82:1-7: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 66, but without a corresponding object release within this function.
Signed-off-by: Wen Yang <wen.yang99@zte.com.cn>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Tomasz Figa <tomasz.figa@gmail.com>
Cc: Sylwester Nawrocki <s.nawrocki@samsung.com>
Cc: Kukjin Kim <kgene@kernel.org>
Cc: linux-samsung-soc@vger.kernel.org
Cc: linux-gpio@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/samsung/pinctrl-exynos-arm.c

@@ -71,6 +71,7 @@ s5pv210_retention_init(struct samsung_pinctrl_drv_data *drvdata,
 	}
 
 	clk_base = of_iomap(np, 0);
+	of_node_put(np);
 	if (!clk_base) {
 		pr_err("%s: failed to map clock registers\n", __func__);
 		return ERR_PTR(-EINVAL);