of_mm_gpiochip_add_data() calls mm_gc->save_regs() before
setting the data. Therefore ->save_regs() cannot use
gpiochip_get_data()

An Oops is encountered without this fix.

fixes: 1e714e54 ("powerpc: qe_lib-gpio: use gpiochip data pointer")
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: <stable@vger.kernel.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Scott Wood <oss@buserror.net>