[media] vb2: use pr_info instead of pr_debug

Modern kernels enable dynamic printk support, which is fine, except when it is
combined with a debug module option. Enabling debug in videobuf2-core now produces
no debugging unless it is also enabled through the dynamic printk support in debugfs.

Either use a debug module option + pr_info, or use pr_debug without a debug module
option. In this case the fact that you can set various debug levels is very useful,
so I believe that for videobuf2-core.c we should use pr_info.

The mix of the two is very confusing: I've spent too much time already trying to
figure out why I am not seeing any debug output in the kernel log when I do:

	echo 1 >/sys/modules/videobuf2_core/parameters/debug

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