machines: Add new seco-nxp machine override

We need an additional override that has a higher prio than the ones from
meta-freescale but still can be overridden by specific machine overrides
(e.g. seco-mx8mp).
The override is intended for vendor specific config files (e.g.
weston.ini).

conf/machine/include/seconorth-machine.inc

@@ -14,6 +14,8 @@ KBUILD_BUILD_HOST := "seco.com"
 # For more info see meta-freescale/conf/machine/include/imx-base.inc.
 MACHINEOVERRIDES_EXTENDER_FILTER_OUT = " "
 
+MACHINEOVERRIDES =. "seco-nxp:"
+
 MACHINE_EXTRA_RRECOMMENDS:append = " \
     gfxml2dto \
     kernel-modules \