media: vsp1: fix memory leak of dl on error return path

Currently when the call vsp1_dl_body_get fails and returns null the
error return path leaks the allocation of dl. Fix this by kfree'ing
dl before returning.

Addresses-Coverity: ("Resource leak")

Fixes: 5d7936b8 ("media: vsp1: Convert display lists to use new body pool")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>