Integrate meta-seconorth-distro/kirkstone-fix-overrides

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Commit: seco-ne/yocto/layers/meta-seconorth-distro@30e18056

overrides: Fix _ vs : syntax, use mx6, mx6ull and mx8

We reintroduced the plain mx8, mx8mm and mx8mp overrides without
-generic-bsp appendix. This changes the usage back to those.

default.xml

@@ -22,7 +22,7 @@
     <project name="meta-freescale.git"              revision="2fb1ce365338126aad365012ebb913b3e4a9f1be"  remote="fslc"         path="sources/meta-freescale"            />
     <project name="meta-freescale-distro.git"       revision="fc15f5003043da23212596be7366ae2547c308ad"  remote="fslc"         path="sources/meta-freescale-distro"     />
     <project name="layers/meta-seconorth-machine"   revision="6b45accbfb241a00b70ff3121219184e0c96dae3"  remote="seco-ne"      path="sources/meta-seconorth-machine"    />
-    <project name="layers/meta-seconorth-distro"    revision="2dfeed692722329f951de89d59b1d0e711d8aace"  remote="seco-ne"      path="sources/meta-seconorth-distro"     />
+    <project name="layers/meta-seconorth-distro"    revision="30e18056cb2ee226f5533ad6c1b20c460aeace7c"  remote="seco-ne"      path="sources/meta-seconorth-distro"     />
     <project name="layers/meta-seconorth-nogplv3"   revision="546c2e50c656581655b538a3e08c797d9bd8eaca"  remote="seco-ne"      path="sources/meta-seconorth-nogplv3"    />
     <project name="config"                          revision="d3eac4869dd26cdbcc50557c209b858330296505"  remote="seco-ne"      path=".conf"                              >
         <linkfile dest="setup-environment" src="setup-environment" />