Build fix: consumer: unused-but-set-variable warning

clang 15.0.7 produces the following warning, preventing the build of the
project with -Werror:

  consumer/consumer.cpp:2519:15: error: variable 'num_hup' set but not used [-Werror,-Wunused-but-set-variable]
          int num_rdy, num_hup, high_prio, ret, i, err = -1;
                       ^

num_hup is indeed not used, so remove its declaration and its
assignations.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Change-Id: Iccd8aa7716602d6babd1ed5aa23d06268385480c