use XEN_SYSCTL_SCHEDOP_* for sysctl operation checks

use XEN_SYSCTL_SCHEDOP_* for sysctl operation checks

In flask_sysctl_scheduler_op() and sched_adjust_global() the test for
the desired operation is done with the wrong constants. While the
values are correct, the names are not.

Correct the error message for the case of an unknown operation in
flask_sysctl_scheduler_op(), too.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: George Dunlap <george.dunlap@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>