fix warning in drivers/net/appletalk/cops.c

drivers/net/appletalk/cops.c: In function ‘cops_reset’:
drivers/net/appletalk/cops.c:507: warning: comparison of distinct pointer
types lacks a cast

by replacing hand-woven msleep() with call to msleep()

Signed-off-by: Jeff Garzik <jgarzik@redhat.com>