linux-yocto-rt: add qemumips and qemuppc to COMPATIBLE_MACHINES

3.10-rt boots and has good cyclictest results on qemuppc and qemumips,
so we can now safely add them into COMPATIBLE_MACHINES.

Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>