KVM: PPC: Reimplement LOAD_VSX/STORE_VSX instruction mmio emulation with analyse_instr() input

This patch reimplements LOAD_VSX/STORE_VSX instruction MMIO emulation with
analyse_instr() input. It utilizes VSX_FPCONV/VSX_SPLAT/SIGNEXT exported
by analyse_instr() and handle accordingly.

When emulating VSX store, the VSX reg will need to be flushed so that
the right reg val can be retrieved before writing to IO MEM.

[paulus@ozlabs.org - mask the register number to 5 bits.]

Suggested-by: Paul Mackerras <paulus@ozlabs.org>
Signed-off-by: Simon Guo <wei.guo.simon@gmail.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>