Adpated to the new environment file name for powerpc, due to the oe-core
commit c2d96179.
Fixed bug [YOCTO #2055].
(From OE-Core rev: bebcac5e6eaceb7bdafa6432e42fe8073a42c6d2)
Signed-off-by: Lianhao Lu <lianhao.lu@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>