config: lxc: enable KERNEL_POSIX_MQUEUE

Recent lxc versions are not useful if this option is not enabled. That said,
enable KERNEL_POSIX_MQUEUE by default when KERNEL_LXC_MISC is selected.

Signed-off-by: Luka Perkov <luka@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@39385 3c298f89-4303-0410-b956-a3cf2f4a3e73