Fix various gcc 8 compiler warnings related to ARRAY_SIZE.

Fix various gcc 8 compiler warnings related to ARRAY_SIZE.

Example:

  In file included from src/hardware/kecheng-kc-330b/protocol.h:26,
                   from src/hardware/kecheng-kc-330b/api.c:22:
  src/hardware/kecheng-kc-330b/api.c: In function ‘config_list’:
  src/libsigrok-internal.h:51:34: warning: division ‘sizeof (void *) / sizeof (void)’ does not compute the number of array elements [-Wsizeof-pointer-div]
   #define ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0]))
                                    ^
  src/libsigrok-internal.h:55:32: note: in expansion of macro ‘ARRAY_SIZE’
   #define ARRAY_AND_SIZE(a) (a), ARRAY_SIZE(a)
                                  ^~~~~~~~~~
  src/libsigrok-internal.h:964:43: note: in expansion of macro ‘ARRAY_AND_SIZE’
    std_opts_config_list(key, data, sdi, cg, ARRAY_AND_SIZE(scanopts), \
                                             ^~~~~~~~~~~~~~
  src/hardware/kecheng-kc-330b/api.c:296:10: note: in expansion of macro ‘STD_CONFIG_LIST’
     return STD_CONFIG_LIST(key, data, sdi, cg, NULL, drvopts, devopts);
            ^~~~~~~~~~~~~~~