media: dib0700: fix locking in dib0700_i2c_xfer_new()

This patch mostly adds unlocks to error paths.  But one additional small
change is that I made the first "break;" a "goto unlock;" which means
that now we return failure instead of success on that path.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>