cifs.upcall: fix compile warning

cifs.upcall: fix compile warning

Steve French noticed these warnings when building cifs.upcall:

   Compiling client/cifs.upcall.c
   client/cifs.upcall.c: In function 'usage':
   client/cifs.upcall.c:204: warning: declaration of 'prog' shadows a global declaration
   client/cifs.upcall.c:33: warning: shadowed declaration is here

Change the usage function to not take and arg and have it just use the global
"prog" variable. Fix a typo in the log message generated when an unknown
option is specified. Also getopt() always returns '?' when it sees an unknown
option so there's no point in printing it out.

Signed-off-by: Jeff Layton <jlayton@redhat.com>