.travis.yml: reduce the module builds to major architectures

The --enable-modules build is consistently tripping the time limit so
reduce our target list to the "major" architectures.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

.travis.yml

@@ -98,8 +98,9 @@ matrix:
         - CONFIG="--disable-linux-aio --disable-cap-ng --disable-attr --disable-brlapi --disable-libusb --disable-user --disable-replication"
 
 
+    # Module builds are mostly of interest to major distros
     - env:
-        - CONFIG="--enable-modules --disable-linux-user"
+        - CONFIG="--enable-modules --target-list=aarch64-softmmu,arm-softmmu,i386-softmmu,mips-softmmu,mips64-softmmu,ppc64-softmmu,riscv64-softmmu,s390x-softmmu,x86_64-softmmu"
 
 
     # Alternate coroutines implementations are only really of interest to KVM users