target-sparc: fix 32-bit truncation in fpackfix

This is reported by Coverity.  The algorithm description at
ftp://ftp.icm.edu.pl/packages/ggi/doc/hw/sparc/Sparc.pdf suggests
that the 32-bit parts of rs2, after the left shift, is treated
as a 64-bit integer.  Bits 32 and above are used to do the
saturating truncation.

Message-Id: <1446473134-4330-1-git-send-email-pbonzini@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

target-sparc/vis_helper.c

@@ -447,7 +447,7 @@ uint32_t helper_fpackfix(uint64_t gsr, uint64_t rs2)
     for (word = 0; word < 2; word++) {
         uint32_t val;
         int32_t src = rs2 >> (word * 32);
-        int64_t scaled = src << scale;
+        int64_t scaled = (int64_t)src << scale;
         int64_t from_fixed = scaled >> 16;
 
         val = (from_fixed < -32768 ? -32768 :