target-mips: fix for sign-issue in MULQ_W helper

Correct sign-propagation before multiplication in MULQ_W helper.
The change also fixes previously incorrect expected values in the
tests for MULQ_RS.W and MULQ_S.W.
Signed-off-by: NPetar Jovanovic <petarj@mips.com>
Richard Henderson <rth@twiddle.net>
Signed-off-by: NAurelien Jarno <aurelien@aurel32.net>
(cherry picked from commit a345481b)
Signed-off-by: NMichael Roth <mdroth@linux.vnet.ibm.com>

target-mips/dsp_helper.c

@@ -2689,7 +2689,7 @@ MAQ_SA_W(maq_sa_w_phr, 0);
 target_ulong helper_##name(target_ulong rs, target_ulong rt,   \
                            CPUMIPSState *env)                  \
 {                                                              \
-    uint32_t rs_t, rt_t;                                       \
+    int32_t rs_t, rt_t;                                        \
     int32_t tempI;                                             \
     int64_t tempL;                                             \
                                                                \

tests/tcg/mips/mips32-dspr2/mulq_rs_w.c

@@ -8,7 +8,7 @@ int main()
 
     rs = 0x80001234;
     rt = 0x80004321;
-    result = 0x80005555;
+    result = 0x7FFFAAAB;
 
     __asm
         ("mulq_rs.w %0, %1, %2\n\t"

tests/tcg/mips/mips32-dspr2/mulq_s_w.c

@@ -8,7 +8,7 @@ int main()
 
     rs = 0x80001234;
     rt = 0x80004321;
-    result = 0x80005555;
+    result = 0x7FFFAAAB;
 
     __asm
         ("mulq_s.w %0, %1, %2\n\t"