GBE: Optimize scratch memory usage using register interval

GBE: Optimize scratch memory usage using register interval

As scratch memory is a limited resource in HW. And different
register have the opptunity to share same scratch memory. So
I introduce an allocator for scratch memory management.

v2:
In order to reuse the registerFilePartitioner, I rename it as
SimpleAllocator, and derive ScratchAllocator & RegisterAllocator
from it.

v3:
fix a typo, scratch size is 12KB.

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