pinctrl: simplify check for pin request conflicts

This is a non-functional change, which deletes code duplication in two
of four if-if branches by reordering the checks. Functional identity
of the code change can be shown by running through the whole truth table
of boolean arguments.

Signed-off-by: Vladimir Zapolskiy <vz@mleia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>