pinctrl: exynos5440: Use off-stack memory for pinctrl_gpio_range

The range is registered into a linked list which can be referenced
throughout the lifetime of the driver. Ensure the range's memory is useful
for the same lifetime by adding it to the driver's private data structure.

The bug was introduced in the driver's initial commit, which was present in
v3.10.

Fixes: f0b9a7e5 ("pinctrl: exynos5440: add pinctrl driver for Samsung EXYNOS5440 SoC")
Cc: stable@vger.kernel.org
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Acked-by: Tomasz Figa <tomasz.figa@gmail.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>