pinctrl: msm: Use init_valid_mask exported function

The current code produces XPU violation if get_direction is called just
after the initialization.

Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Acked-by: Timur Tabi <timur@kernel.org>
Tested-by: Jeffrey Hugo <jhugo@codeaurora.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>