travis: Add arm64 to build matrix
travis: Add arm64 to build matrix

Signed-off-by: Geoff Levand <c3918f39022407dee6a0056ceca9b1aa80e8e4ce@infradead.org>

Shashwatsh/rkt,jakon89/rkt,ybubnov/rkt,squeed/rkt,dgonyeo/rkt,yifan-gu/rkt,akshaykarle/rkt,jakon89/rkt,euank/rkt,jonboulle/rkt,rkt/rkt,rkt/rkt,achanda/rkt,shobhit85/rkt,achanda/rkt,lucasallan/rkt,lucasallan/rkt,yifan-gu/rocket,nhlfr/rkt,monstermunchkin/rkt,shobhit85/rkt,monstermunchkin/rkt,akshaykarle/rkt,s-urbaniak/rkt,coreos/rkt,jonboulle/rkt,coreos/rkt,achanda/rkt,yifan-gu/rocket,sstabellini/rkt,nhlfr/rkt,sstabellini/rkt,sgotti/rkt,Wilybald/rkt,ybubnov/rkt,jjlakis/rkt,squeed/rkt,jjlakis/rkt,euank/rkt,joshix/rkt,yifan-gu/rkt,jakon89/rkt,kinvolk/rkt,shobhit85/rkt,jjlakis/rkt,yifan-gu/rocket,kinvolk/rkt,joshix/rkt,alban/rkt,s-urbaniak/rkt,joshix/rkt,nhlfr/rkt,akshaykarle/rkt,kinvolk/rkt,Wilybald/rkt,intelsdi-x/rkt,squeed/rkt,rkt/rkt,lucasallan/rkt,dgonyeo/rkt,lucasallan/rkt,intelsdi-x/rkt,ybubnov/rkt,Wilybald/rkt,cab105/rkt,rkt/rkt,s-urbaniak/rkt,alban/rkt,Shashwatsh/rkt,joshix/rkt,intelsdi-x/rkt,jonboulle/rkt,sgotti/rkt,sstabellini/rkt,Shashwatsh/rkt,sgotti/rkt,cab105/rkt,monstermunchkin/rkt,kinvolk/rkt,coreos/rkt,dgonyeo/rkt,euank/rkt,cab105/rkt,Wilybald/rkt,alban/rkt,yifan-gu/rkt