sample/mdev/mbochs: remove set but not used variable 'mdev_state'

Fixes gcc '-Wunused-but-set-variable' warning:

samples/vfio-mdev/mbochs.c: In function mbochs_ioctl:
samples/vfio-mdev/mbochs.c:1188:21: warning: variable mdev_state set but not used [-Wunused-but-set-variable]

It's not used any more since commit 104c7405 ("vfio:
add edid support to mbochs sample driver")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

samples/vfio-mdev/mbochs.c

@@ -1185,9 +1185,6 @@ static long mbochs_ioctl(struct mdev_device *mdev, unsigned int cmd,
 {
 	int ret = 0;
 	unsigned long minsz, outsz;
-	struct mdev_state *mdev_state;
-
-	mdev_state = mdev_get_drvdata(mdev);
 
 	switch (cmd) {
 	case VFIO_DEVICE_GET_INFO: