GBE: implement uniform analysis.

GBE: implement uniform analysis.

We have many uniform (scalar) input values which include
the kernel input argument and some special registers.

And all those variables derived by all uniform values are
also uniform values. This patch analysis this type of register
at liveness analysis stage, and change uniform register's
type to scalar type. Then latter, these registers need
less register space.

Signed-off-by: Zhigang Gong <zhigang.gong@intel.com>
Reviewed-by: Ruiling Song <ruiling.song@intel.com>