media: solo6x10: Switch to using the new API kobj_to_dev()

fixed the following coccicheck:
./drivers/media/pci/solo6x10/solo6x10-core.c:371:60-61: WARNING
opportunity for kobj_to_dev()

Reported-by: Abaci Robot <[e-mail]>
Signed-off-by: Yang Li <[e-mail]>
Signed-off-by: Hans Verkuil <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/pci/solo6x10/solo6x10-core.c

···
 			  struct bin_attribute *a, char *buf,
 			  loff_t off, size_t count)
 {
-	struct device *dev = container_of(kobj, struct device, kobj);
+	struct device *dev = kobj_to_dev(kobj);
 	struct solo_dev *solo_dev =
 		container_of(dev, struct solo_dev, dev);
 	const int size = solo_dev->sdram_size;