media: davinci: vpif_capture: add NULL check on devm_kzalloc return value

[ Upstream commit 5a18c2434f8bfc8bc2fb0f8af3e44f7408d63e4f ]

Check return value from call to devm_kzalloc() in order to prevent
a NULL pointer dereference.

This issue was detected with the help of Coccinelle.

Fixes: 4a5f8ae5 ("[media] davinci: vpif_capture: get subdevs from DT when available")

Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>