cyclic: Don't disable cylic function upon exceeding CPU time

With the migration of the watchdog infrastructure to cyclic functions
it's been noticed, that at least one watchdog driver is broken now. As
the execution time of it's watchdog reset function is quite long.

In general it's not really necessary (right now) to disable the cyclic
function upon exceeding CPU time usage. So instead of disabling the
cylic function in this case, let's just print a warning once to show
this potential problem to the user.

Signed-off-by: Stefan Roese <sr@denx.de>
Suggested-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Cc: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Cc: Tom Rini <trini@konsulko.com>
Cc: Pali Rohár <pali@kernel.org>