LU-5687 dt: propagate errors from failed declarations

LU-5687 dt: propagate errors from failed declarations

Check for and return errors from dt_declare_*() in several locations.

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Change-Id: Id18b12d6c713e78e2f1cc782ff659d2c84cc60bb
Reviewed-on: http://review.whamcloud.com/12130
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Mike Pershin <mike.pershin@intel.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>