staging: vc04_services: Change fields of page list structure to fixed length

The arm processor core and the GPU have shared data structures.
One of these structures is a list of pages of data for messages.
This structure can not change since it is dependent on the GPU
firmware which is external to the kernel.  Convert the fields
of this structure to fixed length fields.

Signed-off-by: Michael Zoran <mzoran@crowfest.net>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>