mic: vop: Cast pointers to unsigned long

Fix these on 32-bit:

 vop_vringh.c:711:13: error: cast from pointer to integer of different
 size [-Werror=pointer-to-int-cast]

Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>