The generic IRQ helper library just checks if the IRQ line is
set as input before activating it for interrupts. As we
recently started to check things better with .get_dir() it
turns out that it's good to try to convince the line to become
an input before attempting to lock it as IRQ.
Reviewed-by: NBjörn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>