travis: Exclude MIPS from the bcm job

We don't need to pull in anything from the MIPS job so exclude that from
the new bcm job and make it clear it's building only ARM.
Signed-off-by: NTom Rini <trini@konsulko.com>

.travis.yml

@@ -180,9 +180,9 @@ matrix:
     - name: "buildman boundary engicam toradex"
       env:
         - BUILDMAN="boundary engicam toradex"
-    - name: "buildman bcm"
+    - name: "buildman ARM bcm"
       env:
-        - BUILDMAN="bcm"
+        - BUILDMAN="bcm -x mips"
     - name: "buildman NXP ARM32"
       env:
         - BUILDMAN="freescale -x powerpc,m68k,aarch64"