media: omap_vout: Fix a possible null pointer dereference in omap_vout_open()

Move a debug message so that a null pointer access can not happen
for the variable "vout" in this function.

Fixes: 5c7ab634 ("V4L/DVB: V4L2: Add support for OMAP2/3 V4L2 display driver on top of DSS2")

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>