pinctrl: axp209: dereference pointer after it's been set

The number of GPIOs is gotten from a field within the structure
referenced in the of_device.data but it was actually read before it was
retrieved, thus it was dereferencing a null pointer.

Set the number of GPIOs after retrieving of_device.data.

Fixes: e1190083 ("pinctrl: axp209: add support for AXP813 GPIOs")
Signed-off-by: Quentin Schulz <quentin.schulz@free-electrons.com>
Reported-by: Mylène Josserand <mylene.josserand@free-electrons.com>
Tested-by: Mylène Josserand <mylene.josserand@free-electrons.com>
Acked-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>