fotg210-udc: Introduce and use a fotg210_ack_int function

This is in preparation of support for devices where interrupts are acked
differently.

Signed-off-by: Fabian Vogt <fabian@ritter-vogt.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20230123073508.2350402-3-linus.walleij@linaro.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>