Changes requirement for "vsubsbs" instruction

Changes requirement for "vsubsbs" instruction, which has been supported
since ISA 2.03. (Please see section 5.9.1.2 of ISA 2.03)

Reported-by: Paul A. Clarke <pc@us.ibm.com>
Signed-off-by: Paul A. Clarke <pc@us.ibm.com>
Signed-off-by: Leonardo Bras <leonardo@linux.vnet.ibm.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
(cherry picked from commit fcfbc18)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

target/ppc/translate/vmx-ops.inc.c

@@ -143,7 +143,7 @@ GEN_VXFORM(vaddsws, 0, 14),
 GEN_VXFORM_DUAL(vsububs, bcdadd, 0, 24, PPC_ALTIVEC, PPC_NONE),
 GEN_VXFORM_DUAL(vsubuhs, bcdsub, 0, 25, PPC_ALTIVEC, PPC_NONE),
 GEN_VXFORM(vsubuws, 0, 26),
-GEN_VXFORM_DUAL(vsubsbs, bcdtrunc, 0, 28, PPC_NONE, PPC2_ISA300),
+GEN_VXFORM_DUAL(vsubsbs, bcdtrunc, 0, 28, PPC_ALTIVEC, PPC2_ISA300),
 GEN_VXFORM(vsubshs, 0, 29),
 GEN_VXFORM_DUAL(vsubsws, xpnd04_2, 0, 30, PPC_ALTIVEC, PPC_NONE),
 GEN_VXFORM_207(vadduqm, 0, 4),