Make SpaceBitmap cross-compiling tolerant

Change the order of bits in SpaceBitmap to be the intuitive one:
Offset 0 is bit 0, instead of the MSB. Then compiling on 32b for
64b works as expected.

Change-Id: Iee2491eaf06d4b5f8b534b7c980d5719633cb64c
3 files changed