[media] cobalt: fix sparse warnings

drivers/media/pci/cobalt/cobalt-i2c.c:130:17: warning: dereference of noderef expression
drivers/media/pci/cobalt/cobalt-i2c.c:147:17: warning: dereference of noderef expression
drivers/media/pci/cobalt/cobalt-i2c.c:151:26: warning: dereference of noderef expression
drivers/media/pci/cobalt/cobalt-i2c.c:156:34: warning: dereference of noderef expression
drivers/media/pci/cobalt/cobalt-i2c.c:206:17: warning: dereference of noderef expression
drivers/media/pci/cobalt/cobalt-i2c.c:210:26: warning: dereference of noderef expression
drivers/media/pci/cobalt/cobalt-i2c.c:215:34: warning: dereference of noderef expression
drivers/media/pci/cobalt/cobalt-i2c.c:225:27: warning: dereference of noderef expression
drivers/media/pci/cobalt/cobalt-i2c.c:335:17: warning: dereference of noderef expression
drivers/media/pci/cobalt/cobalt-i2c.c:336:17: warning: dereference of noderef expression
drivers/media/pci/cobalt/cobalt-i2c.c:337:17: warning: dereference of noderef expression
drivers/media/pci/cobalt/cobalt-i2c.c:348:34: warning: dereference of noderef expression
drivers/media/pci/cobalt/cobalt-i2c.c:352:17: warning: dereference of noderef expression
drivers/media/pci/cobalt/cobalt-i2c.c:353:17: warning: dereference of noderef expression
drivers/media/pci/cobalt/cobalt-i2c.c:356:17: warning: dereference of noderef expression
drivers/media/pci/cobalt/cobalt-i2c.c:357:17: warning: dereference of noderef expression
drivers/media/pci/cobalt/cobalt-i2c.c:359:17: warning: dereference of noderef expression

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>