pinctrl: stm32: return errors from stm32_gpio_direction_output()

In the STMicroelectronics STM32 driver, stm32_gpio_direction_output()
ignores the result of pinctrl_gpio_direction_output() for no good reason.
Let's propagate errors from pinctrl_gpio_direction_output() upstream...

Found by Linux Verification Center (linuxtesting.org) with the Svace static
analysis tool.

Signed-off-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Link: https://lore.kernel.org/r/5ce023a8-db0c-13a9-be42-09e3348ca44d@omp.ru


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>