Opcode and xopcode are useful definitions not just for KVM. Move these
definitions to asm/ppc-opcode.h for public use.

Also add the opcodes for LHAUX and LWZUX.
Signed-off-by: NJia Hongtao <hongtao.jia@freescale.com>
Signed-off-by: NLi Yang <leoli@freescale.com>
[scottwood@freesacle.com: update commit message and rebase]
Signed-off-by: NScott Wood <scottwood@freescale.com>