powerpc: Fix event-scan code for 32-bit CHRP

On CHRP machines we are supposed to call into firmware (RTAS)
periodically, to give it a chance to check for errors and other
events.  Under ppc we had some special code in timer_interrupt
to do this, but that didn't get transferred over to arch/powerpc.
Instead, we use an array of timer_list structs, one per CPU,
and use add_timer_on to make sure each one gets called on the
appropriate CPU.

With this we can remove the heartbeat_* elements of the ppc_md
struct.

Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/platforms/chrp/chrp.h

@@ -8,4 +8,4 @@ extern int chrp_set_rtc_time(struct rtc_time *);
 extern long chrp_time_init(void);
 
 extern void chrp_find_bridges(void);
-extern void chrp_event_scan(void);
+extern void chrp_event_scan(unsigned long);