doc: fix a typo about irq affinity

smp_affinity holds bitmask and smp_affinity_list holds list. So we
should write a list to smp_affinity_list, instead of smp_affinity.

Signed-off-by: Hu Tao <[e-mail]>
Acked-by: Rob Landley <[e-mail]>
Signed-off-by: Jiri Kosina <[e-mail]>

Documentation/IRQ-affinity.txt

···
 
 Here is an example of limiting that same irq (44) to cpus 1024 to 1031:
 
-[root@moon 44]# echo 1024-1031 > smp_affinity
-[root@moon 44]# cat smp_affinity
+[root@moon 44]# echo 1024-1031 > smp_affinity_list
+[root@moon 44]# cat smp_affinity_list
 1024-1031
 
 Note that to do this with a bitmask would require 32 bitmasks of zero