finish VPATH -> vpath translation

This adds a few more vpath suffixes and points the remaining two paths
explicitly to $(SRC_PATH) in order to eliminate the VPATH assignment
from config-host.mak.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: Juan Quintela <quintela@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>