[CORE] Don't include vmm_chardev.h in vmm_heap.h

The vmm_heap.h is included at large number of places. Any header
included in vmm_heap.h will be indirectly included at number of
places.

To force explicit include of vmm_chardev.h we remove it from
vmm_heap.h

Also, we do minor consmetic changes in vmm_heap_print_state().

Signed-off-by: Anup Patel <anup@brainfault.org>