npp: use proper format for integers (-Wformat)

Properly print signed and unsigned integers.  This fixes warnings like:

    In file included from plugins/npp.c:36:
    plugins/npp.c: In function ‘npp_push’:
    ./include/near/log.h:45:14: error: format ‘%zd’ expects argument of type ‘signed size_t’, but argument 4 has type ‘size_t’ {aka ‘long unsigned int’} [-Werror=format=]
       45 |   near_debug("%s:%s() " fmt, \
          |              ^~~~~~~~~~
    plugins/npp.c:185:2: note: in expansion of macro ‘DBG’
      185 |  DBG("Sending %zd bytes", frame_length);
          |  ^~~

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
1 file changed