config: kernel: only enable container features if !SMALL_FLASH

config: kernel: only enable container features if !SMALL_FLASH

KERNEL_DEVPTS_MULTIPLE_INSTANCES and KERNEL_POSIX_MQUEUE were
previously enabled by default only if KERNEL_LXC_MISC was selected.
KERNEL_LXC_MISC was enabled only if the SMALL_FLASH (anti-)feature
was not selected.
Now that KERNEL_LXC_MISC no longer exists, make sure that those
options are also only enabled by default for !SMALL_FLASH targets.

Fixes: 4f94a331 ("config: kernel: remove KERNEL_LXC_MISC")
Signed-off-by: Daniel Golle <daniel@makrotopia.org>