hw/intc/arm_gicv3_its: Avoid maybe-uninitialized error in get_vte()

hw/intc/arm_gicv3_its: Avoid maybe-uninitialized error in get_vte()

Fix when using GCC v11.4 (Ubuntu 11.4.0-1ubuntu1~22.04) with CFLAGS=-Og:

  [4/6] Compiling C object libcommon.fa.p/hw_intc_arm_gicv3_its.c.o
  FAILED: libcommon.fa.p/hw_intc_arm_gicv3_its.c.o
      inlined from ‘lookup_vte’ at hw/intc/arm_gicv3_its.c:453:9,
      inlined from ‘vmovp_callback’ at hw/intc/arm_gicv3_its.c:1039:14:
  hw/intc/arm_gicv3_its.c:347:9: error: ‘vte.rdbase’ may be used uninitialized [-Werror=maybe-uninitialized]
    347 |         trace_gicv3_its_vte_read(vpeid, vte->valid, vte->vptsize,
        |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    348 |                                  vte->vptaddr, vte->rdbase);
        |                                  ~~~~~~~~~~~~~~~~~~~~~~~~~~
  hw/intc/arm_gicv3_its.c: In function ‘vmovp_callback’:
  hw/intc/arm_gicv3_its.c:1036:13: note: ‘vte’ declared here
   1036 |     VTEntry vte;
        |             ^~~

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 20230831131348.69032-1-philmd@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>