wifi: plfxlc: Drop unused include

The driver includes the legacy GPIO header <linux/gpio.h>
but does not use any symbols from it. Drop the include.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://msgid.link/20240131-descriptors-wireless-v1-5-e1c7c5d68746@linaro.org