media: staging: imx-media-vdic: fix inconsistent IS_ERR and PTR_ERR

Fix inconsistent IS_ERR and PTR_ERR in vdic_get_ipu_resources.
The proper pointer to be passed as argument is ch.

This issue was detected with the help of Coccinelle.

Fixes: 0b2e9e79

 ("media: staging/imx: remove confusing IS_ERR_OR_NULL usage")

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Acked-by: Steve Longerbeam <steve_longerbeam@mentor.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>