winsys/virgl: correct resource and handle allocation (v2)

Fixes crash with
  piglit/bin/map_buffer_range-invalidate CopyBufferSubData \
                               increment-offset -auto -fbo

* Resize the resource storage already when the count is equal to the
  allocated size, fixes:

  Invalid write of size 8
  at 0xB72E4CF: virgl_drm_add_res (virgl_drm_winsys.c:629)
  by 0xB72E4CF: virgl_drm_emit_res (virgl_drm_winsys.c:663)
  by 0xB72A44A: virgl_encode_resource_copy_region (virgl_encode.c:776)
  by 0xB40CD12: st_copy_buffer_subdata (st_cb_bufferobjects.c:585)
  by 0xB244A3B: _mesa_CopyBufferSubData (bufferobj.c:2940)
  by 0x109A1E: upload (invalidate.c:169)
  by 0x109C2F: piglit_display (invalidate.c:215)
  by 0x4F80FBE: run_test (piglit_fbo_framework.c:52)
  by 0x4F66E5F: piglit_gl_test_run (piglit-framework-gl.c:229)
  by 0x10949D: main (invalidate.c:47)
  Address 0xbe07d30 is 0 bytes after a block of size 4,096 alloc'd
  at 0x4C31B25: calloc (in
       /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
  by 0xB72DAAF: virgl_drm_cmd_buf_create (virgl_drm_winsys.c:567)

* Also resize the space allocated for the handles, fixes:

  Invalid write of size 4
  at 0xB72E4F0: virgl_drm_add_res (virgl_drm_winsys.c:631)
  by 0xB72E4F0: virgl_drm_emit_res (virgl_drm_winsys.c:663)
  by 0xB72A44A: virgl_encode_resource_copy_region (virgl_encode.c:776)
  by 0xB40CD12: st_copy_buffer_subdata (st_cb_bufferobjects.c:585)
  by 0xB244A3B: _mesa_CopyBufferSubData (bufferobj.c:2940)
  by 0x109A1E: upload (invalidate.c:169)
  by 0x109C2F: piglit_display (invalidate.c:215)
  by 0x4F80FBE: run_test (piglit_fbo_framework.c:52)
  by 0x4F66E5F: piglit_gl_test_run (piglit-framework-gl.c:229)
  by 0x10949D: main (invalidate.c:47)
  Address 0xbe08570 is 0 bytes after a block of size 2,048 alloc'd
  at 0x4C2FB0F: malloc (
    in /usr/lib/valgrind/vgpreload_memcheck-amd64- linux.so)
  by 0xB72DAC8: virgl_drm_cmd_buf_create (virgl_drm_winsys.c:572)

Fixes: 4b15b5e8 ("virgl: resize resource bo allocation if we need to.")

v2: - Use REALLOC macro and avoid memory leak when re-allocation fails
    - add Fixes tag (both Emil Velikov)
    - reorder commit message

Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
(cherry picked from commit 9b0e8d87)