staging: unisys: fix CamelCase global variables in file.c

Fix CamelCase names:

Cdev => file_cdev
PControlVm_channel => file_controlvm_channel
MajorDev => majordev
Registered => registered

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