Fix casts of pointers to integers of different sizes in the ivtv framebuffer
driver.

These were introduced in patch 38eb6ba5b8487d15b020fe391d324edd2b659b03.
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Signed-off-by: NHans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: NMauro Carvalho Chehab <mchehab@infradead.org>