gpio: htc-egpio: Remove unused exported htc_egpio_get_wakeup_irq()

This function was never used upstream, and is a relic of the original
handhelds.org code the htc-egpio driver was based on.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20190910141529.21030-1-geert+renesas@glider.be


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