libdvbv5/descriptors.c: fix two warnings

libdvbv5/descriptors.c: fix two warnings

descriptors.c:134:4: warning: format '%ld' expects argument of type 'long int', but argument 4 has type 'int' [-Wformat=]
    dvb_logwarn("descriptor type 0x%02x is truncated: desc len %ld, section len %zd",
    ^
descriptors/desc_frequency_list.c: In function 'dvb_desc_frequency_list_init':
descriptors/desc_frequency_list.c:31:12: warning: initialization discards 'const' qualifier from pointer target type [enabled by default]
  char *p = buf;

Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>