gpio: virtio: remove unneeded semicolon

Eliminate the following coccicheck warning:
./drivers/gpio/gpio-virtio.c:437:2-3: Unneeded semicolon

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>