qemu-cortex-m3: new MACHINE

Various changes to properly handle QEMU for Cortex M3.
This was solved by creating a new MACHINE qemu-cortex-m3.
Specifying MACHINE=qemu-cortex-m3 will select proper tuning
for the cross-compiler.

Typical usage:

    $ MACHINE=qemu-cortex-m3 bitbake zephyr-philosophers

Signed-off-by: Juro Bystricky <juro.bystricky@intel.com>

lib/oeqa/utils/qemuzephyrrunner.py

@@ -68,7 +68,7 @@ class QemuZephyrRunner(QemuRunner):
 
         self.qemuparams = '-nographic -serial unix:%s,server' % (self.socketname)
         qemu_binary = ""
-        if 'arm' in self.machine:
+        if 'arm' in self.machine or 'cortex' in self.machine:
             qemu_binary = 'qemu-system-arm'
             qemu_machine_args = '-machine lm3s6965evb'
         elif 'x86' in self.machine: