Remove duplicate submodule update command from travis config.
Remove duplicate submodule update command from travis config.

Looks like travis arleady runs "git submodule update". Plus this line was
missing "git".

ene-ilies/vi-firmware,mgiannikouris/vi-firmware,openxc/vi-firmware,ene-ilies/vi-firmware,openxc/vi-firmware,mgiannikouris/vi-firmware,ene-ilies/vi-firmware,openxc/vi-firmware,mgiannikouris/vi-firmware,openxc/vi-firmware,mgiannikouris/vi-firmware,ene-ilies/vi-firmware