media: davinci/vpif.c: drop unnecessary cast

DEFINE_RES_IRQ_NAMED already casts to (struct resource), so no
need to do it again.

This fixes a sparse warning:

vpif.c:483:20: warning: cast to non-scalar

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Cc: "Lad, Prabhakar" <prabhakar.csengg@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>