gpio: of: Optimize quirk checks

Simple string comparisons are cheaper than DT lookups, as the latter
involve taking a spinlock and traversing properties.
Hence optimize quirk checks by postponing DT lookups after string
comparisons.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>