build: include config-{, all-}devices.mak after defining CONFIG_SOFTMMU and CONFIG_USER_ONLY

Moving the inclusions closer to Makefile, and before rules.mak, makes
Makefile and Makefile.target more consistent with each other.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Tested-by: Markus Armbruster <armbru@redhat.com>
Message-id: 1366102238-12374-1-git-send-email-pbonzini@redhat.com
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>