hw/display/xlnx_dp: Free FIFOs adding xlnx_dp_finalize()

hw/display/xlnx_dp: Free FIFOs adding xlnx_dp_finalize()

When building with --enable-sanitizers we get:

  Direct leak of 16 byte(s) in 1 object(s) allocated from:
      #0 0x5618479ec7cf in malloc (qemu-system-aarch64+0x233b7cf)
      #1 0x7f675745f958 in g_malloc (/lib64/libglib-2.0.so.0+0x58958)
      #2 0x561847c2dcc9 in xlnx_dp_init hw/display/xlnx_dp.c:1259:5
      #3 0x56184a5bdab8 in object_init_with_type qom/object.c:375:9
      #4 0x56184a5a2bda in object_initialize_with_type qom/object.c:517:5
      #5 0x56184a5a24d5 in object_initialize qom/object.c:536:5
      #6 0x56184a5a2f6c in object_initialize_child_with_propsv qom/object.c:566:5
      #7 0x56184a5a2e60 in object_initialize_child_with_props qom/object.c:549:10
      #8 0x56184a5a3a1e in object_initialize_child_internal qom/object.c:603:5
      #9 0x5618495aa431 in xlnx_zynqmp_init hw/arm/xlnx-zynqmp.c:273:5

The RX/TX FIFOs are created in xlnx_dp_init(), add xlnx_dp_finalize()
to destroy them.

Fixes: 58ac482a66d ("introduce xlnx-dp")
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20210323182958.277654-1-f4bug@amsat.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>