Staging: cpc-usb: depends on PROC_FS

Fix this build error when PROC_FS is not enabled:
cpc-usb_drv.c:61:2: error: #error "PROCFS needed"
cpc-usb_drv.c:1159: error: implicit declaration of function 'proc_mkdir'

Signed-off-by: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>