libcli: Fix maybe-uninitialized warning

libcli: Fix maybe-uninitialized warning

../../libcli/wsp/wsp_aqs.c: In function ‘create_size_range_shortcut’:
../../libcli/wsp/wsp_aqs.c:872:37: error: ‘upper_size’ may be used uninitialized [-Werror=maybe-uninitialized]
  872 |                 right->value.number = upper_size;
      |                 ~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~
../../libcli/wsp/wsp_aqs.c:835:18: note: ‘upper_size’ was declared here
  835 |         uint32_t upper_size;
      |                  ^~~~~~~~~~
cc1: all warnings being treated as errors

Signed-off-by: Jennifer Sutton <jennifersutton@catalyst.net.nz>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>