logger: fix compiler warning, const facilitynames

logger: fix compiler warning, const facilitynames

This was the warning on FreeBSD:
misc-utils/logger.c:221:24: warning: passing 'const CODE [25]' to parameter of type 'CODE *' (aka 'struct _code *') discards qualifiers
      [-Wincompatible-pointer-types-discards-qualifiers]
                facility = decode(s, facilitynames);
                                     ^~~~~~~~~~~~~
misc-utils/logger.c:187:43: note: passing argument to parameter 'codetab' here
static int decode(const char *name, CODE *codetab)

Signed-off-by: Ruediger Meier <ruediger.meier@ga-group.nl>