fix: "smp_call_function: get rid of the unused nonatomic/retry argument"

drivers/char/sysrq.c: In function 'sysrq_showregs_othercpus':
drivers/char/sysrq.c:218: error: too many arguments to function 'smp_call_function'

Signed-off-by: Ingo Molnar <mingo@elte.hu>