FreeBSD: Always include sys/sysctl.h for FreeBSD platform
The drm code for FreeBSD always use sysctl(3) to get information about DRI driver so always include sys/syctl.h for FreeBSD platform. Also include sys/types.h as it's mandatory to use sysctl(3) as stated in the manpage. While here, remove HAVE_SYS_SYSCTL_H check in meson, sysctl is only used in FreeBSD code so it's mandatory.
Signed-off-by: Emmanuel Vadot manu@FreeBSD.org