[PowerPC] bus_space cleanup part 1 - rename bs_be / bs_le functions

[PowerPC] bus_space cleanup part 1 - rename bs_be / bs_le functions

The intention of the bus_be naming was for those to be the no-endian-swapping
and for the bus_le to be endian-swapping in all the functions.

This naming breaks down when we're actually are running in LE and need to
use the opposite sense.

As such, rename bs_be_* to native_bs_* and rename bs_le_* to swapped_bs_*.

No functional change.

Sponsored by:	Tag1 Consulting, Inc.