Add makefile dependencies for target specific device configs.
These will copy the default config if none exists, obsoleting the old
configure time code.  If a config already exists but is older than the
default then print a warning.

Also remove config-devices.h.  Code does not and should not care which
devices are being built.

Signed-off-by: Paul Brook <paul@codesourcery.com>

Generate config-devices.h for each target and config-all-devices.h for
common library.  We don't want to name both config-devices.h to avoid
path problems

Patchworks-ID: 35195
Signed-off-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

Add config.h file that includes config-target.h and config-host.h

Patchworks-ID: 35193
Signed-off-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>