target-ppc: fix vcipher, vcipherlast, vncipherlast and vpermxor

target-ppc: fix vcipher, vcipherlast, vncipherlast and vpermxor

For vector instructions, the helpers get pointers to the vector register
in arguments. Some operands might point to the same register, including
the operand holding the result.

When emulating instructions which access the vector elements in a
non-linear way, we need to store the result in an temporary variable.

This fixes openssl when emulating a POWER8 CPU.

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Alexander Graf <agraf@suse.de>
(cherry picked from commit 65cf1f65be0fc4883edbd66feeab3ddaceb11c00)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>