dma/xlnx-zdma: Populate DBG0.CMN_BUF_FREE

Populate DBG0.CMN_BUF_FREE so that SW can see some free space.

Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Francisco Iglesias <frasse.iglesias@gmail.com>
Message-id: 20200402134721.27863-3-edgar.iglesias@gmail.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/dma/xlnx-zdma.c

@@ -680,6 +680,12 @@ static RegisterAccessInfo zdma_regs_info[] = {
     },{ .name = "ZDMA_CH_DBG0",  .addr = A_ZDMA_CH_DBG0,
         .rsvd = 0xfffffe00,
         .ro = 0x1ff,
+
+        /*
+         * There's SW out there that will check the debug regs for free space.
+         * Claim that we always have 0x100 free.
+         */
+        .reset = 0x100
     },{ .name = "ZDMA_CH_DBG1",  .addr = A_ZDMA_CH_DBG1,
         .rsvd = 0xfffffe00,
         .ro = 0x1ff,