genxml: Make X/Y Offset field of SURFACE_STATE a uint

genxml: Make X/Y Offset field of SURFACE_STATE a uint

THe offset type has special implications that it's intended to be some form
of aligned memory address.  These assumptions allow it to handle the case
where there is some alignment requirement on the offset and the bottom bits
are used for other things.  However, the offsets in the surface state field
are really just unsigned integers.

Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Chad Versace <chad.versace@intel.com>