powerpc/booke: Handle misaligned floating point loads/stores as on AIM

Misaligned floating point loads and stores are already handled for AIM, but
use the DSISR to obtain the necessary data. Book-E does not have the DSISR,
so these fixups are not performed, leading to a SIGBUS on misaligned FP
loads or stores. Obtain the necessary data on the Book-E side, similar to
how is done for SPE.

MFC after: 1 week