net: cadence_gem: Disable TSU feature bit

Disable the Timestamping Unit feature bit since QEMU does not
yet support it. This allows guest SW to correctly probe for
its existance.
Reviewed-by: NAlistair Francis <alistair.francis@wdc.com>
Signed-off-by: NEdgar E. Iglesias <edgar.iglesias@xilinx.com>
Message-id: 20181011021931.4249-2-edgar.iglesias@gmail.com
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

hw/net/cadence_gem.c

@@ -1228,7 +1228,7 @@ static void gem_reset(DeviceState *d)
     s->regs[GEM_MODID] = s->revision;
     s->regs[GEM_DESCONF] = 0x02500111;
     s->regs[GEM_DESCONF2] = 0x2ab13fff;
-    s->regs[GEM_DESCONF5] = 0x002f2145;
+    s->regs[GEM_DESCONF5] = 0x002f2045;
     s->regs[GEM_DESCONF6] = 0x00000200;
 
     /* Set MAC address */