doc: cyclic: remove reference to WATCHDOG_RESET

WATCHDOG_RESET is no more. Replace the reference by schedule().

While here, rearrange the sentence a bit so that "cyclic_run()"
becomes the object and "the main function responsible for calling all
registered cyclic functions" a parenthetical rather than the other way
around, which at least to me makes it more readable.

Signed-off-by: Rasmus Villemoes <[e-mail]>
Reviewed-by: Simon Glass <[e-mail]>
Reviewed-by: Stefan Roese <[e-mail]>

doc/develop/cyclic.rst

···
 How is this cyclic functionality integrated /  executed?
 --------------------------------------------------------
 
-The cyclic infrastructure integrates the main function responsible for
-calling all registered cyclic functions cyclic_run() into the common
-WATCHDOG_RESET macro. This guarantees that cyclic_run() is executed
-very often, which is necessary for the cyclic functions to get scheduled
-and executed at their configured periods.
+The cyclic infrastructure integrates cyclic_run(), the main function
+responsible for calling all registered cyclic functions, into the
+common schedule() function. This guarantees that cyclic_run() is
+executed very often, which is necessary for the cyclic functions to
+get scheduled and executed at their configured periods.