target-arm: Fix VQSHL of signed 64 bit values

Add a missing '-' which meant that we were misinterpreting the shift
argument for VQSHL of 64 bit signed values and treating almost every
shift value as if it were an extremely large right shift.

Signed-off-by: Juha Riihimäki <juha.riihimaki@nokia.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>

target-arm/neon_helper.c

@@ -610,7 +610,7 @@ uint64_t HELPER(neon_qshl_s64)(CPUState *env, uint64_t valop, uint64_t shiftop)
             SET_QC();
             val = (val >> 63) & ~SIGNBIT64;
         }
-    } else if (shift <= 64) {
+    } else if (shift <= -64) {
         val >>= 63;
     } else if (shift < 0) {
         val >>= -shift;