vchiq_2835_arm: suppress warning

Suppress the following warning by casting the pointer to and uintptr_t
before void*:

  drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c: In function ‘vchiq_prepare_bulk_data’:
  drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c:260:15: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
    bulk->data = (void *)VC_SAFE(pagelistinfo->dma_addr);
                 ^

Signed-off-by: Matteo Croce <mcroce@redhat.com>