Let us manage differences of Book-E PowerPC variations i.e. vendor /

Let us manage differences of Book-E PowerPC variations i.e. vendor /
implementation specific vs. the common architecture definition.

Bring PPC4XX defines (PSL, SPR, TLB). Note the new definitions under
BOOKE_PPC4XX are not used in the code yet.

This change set is not supposed to affect existing E500 support, it's just
another reorg step before bringing support for E500mc, E5500 and PPC465.

Obtained from:	AppliedMicro, Freescale, Semihalf