wic: Look for image artifacts in a common location

wic: Look for image artifacts in a common location

Rather than have each image type look for artifacts in image-specific
locations, move towards having them look for artifacts in a common
location, in this case DEPLOY_DIR_IMAGE

Use the existing deploy.bbclass to have the bootloaders put their binaries
in DEPLOY_DIR_IMAGE and then wic will find them and place them in the image

Signed-off-by: Alejandro Hernandez <alejandro.hernandez@linux.intel.com>
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>