target-ppc: Bug: VSX Convert to Integer Should Truncate

The various VSX Convert to Integer instructions should truncate the
floating point number to an integer value, which is equivalent to
a round-to-zero rounding mode.  The existing VSX floating point to
integer conversion helpers are erroneously using the rounding mode set
int the PowerPC Floating Point Status and Control Register (FPSCR).
This change corrects this defect by using the appropriate
float*_to_*_round_to_zero() routines fro the softfloat library.

Signed-off-by: Tom Musta <tommusta@gmail.com>
Tested-by: Tom Musta <tommusta@gmail.com>
Signed-off-by: Alexander Graf <agraf@suse.de>

target-ppc/fpu_helper.c

@@ -2568,7 +2568,8 @@ void helper_##op(CPUPPCState *env, uint32_t opcode)                          \
             fload_invalid_op_excp(env, POWERPC_EXCP_FP_VXCVI, 0);            \
             xt.tfld = rnan;                                                  \
         } else {                                                             \
-            xt.tfld = stp##_to_##ttp(xb.sfld, &env->fp_status);              \
+            xt.tfld = stp##_to_##ttp##_round_to_zero(xb.sfld,                \
+                          &env->fp_status);                                  \
             if (env->fp_status.float_exception_flags & float_flag_invalid) { \
                 fload_invalid_op_excp(env, POWERPC_EXCP_FP_VXCVI, 0);        \
             }                                                                \