rootfs_rpm.bbclass: Reorder feed priority based on multilib image setting

rootfs_rpm.bbclass: Reorder feed priority based on multilib image setting

[ YOCTO #3915 ]
[ CQID: WIND00404309 ]

When doing a multilib image build, such as bitbake lib32-core-image-sato, the
system needs to reorder the priority level of the feeds.  If it does not
reorder the priorities, then 64-bit items can be selected by the automatic
dependency resolution in Smart.

(From OE-Core rev: dfbb1aa184955923b85b81aabf944de8f1a1e4b5)

Signed-off-by: Mark Hatle <mark.hatle@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>