staging: unisys: refactor enum VDISK_MGMT_TYPES

Get rid of the typedef and use enum vdisk_mgmt_types instead. Reformat the
enumeration names and update any references to use the enum directly.

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