In an effort to minimize customer confusion we want to unify naming
convention for VMware-provided kernel modules. This change renames the
balloon driver from vmware_ballon to vmw_balloon.
We expect to follow this naming convention (vmw_<module_name>) for all
modules that are part of mainline kernel and/or being distributed by
VMware, with the sole exception of vmxnet3 driver (since the name of
mainline driver happens to match with the name used in VMware Tools).