xilinx_spips: Make interrupts clear on read

By default these interrupts are clear on read.
Signed-off-by: NPeter Crosthwaite <peter.crosthwaite@xilinx.com>
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NEdgar E. Iglesias <edgar.iglesias@gmail.com>
Message-id: 999ff0091ed3cc3969a431bf55c00ef934cecc8e.1369117359.git.peter.crosthwaite@xilinx.com
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

hw/ssi/xilinx_spips.c

@@ -330,6 +330,10 @@ static uint64_t xilinx_spips_read(void *opaque, hwaddr addr,
         mask = 0x0002FFFF;
         break;
     case R_INTR_STATUS:
+        ret = s->regs[addr] & IXR_ALL;
+        s->regs[addr] = 0;
+        DB_PRINT("addr=" TARGET_FMT_plx " = %x\n", addr * 4, ret);
+        return ret;
     case R_INTR_MASK:
         mask = IXR_ALL;
         break;