staging: unisys: refactor CONTROLVM_MESSAGE_DEVICE_CREATE

Remove the typedef from CONTROLVM_MESSAGE_DEVICE_CREATE, in favor of
struct controlvm_message_device_create, fix CamelCase names, and update
all references.

Header => header
Packet => packet

Signed-off-by: Benjamin Romer <benjamin.romer@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>