If vpif_probe() fails on v4l2_device_register() then memory allocated
at initialize_vpif() for global vpif_obj.dev[i] become unreleased.

The patch adds deallocation of vpif_obj.dev[i] on the error path and
removes duplicated check on platform_data presence.

Found by Linux Driver Verification project (linuxtesting.org).
Signed-off-by: Anton Vasilyev <vasilyev@ispras.ru>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>