dante: Fix compile with glibc

dante: Fix compile with glibc

When compiled with glibc the config_scan.c wants to use the
cpupolicy2numeric() function which is only available when
HAVE_SCHED_SETSCHEDULER is set. It looks like the wrong define was used here.

This fixes a build problem with glibc in combination with the force
ac_cv_func_sched_setscheduler=no in the OpenWrt CONFIGURE_VARS.

This fixes the following compile error with glibc:
----------------------------------------------------------------------
/bin/ld: config_scan.o: in function `socks_yylex':
dante-1.4.1/sockd/config_scan.l:461: undefined reference to `cpupolicy2numeric'
collect2: error: ld returned 1 exit status
make[5]: *** [Makefile:522: sockd] Error 1

Fixes: aaf46a8fe23e ("dante: disable sched_getscheduler() - not implemented in musl")
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>