Fix comment typo in percpu.h

Fix a typo in arch/x86/include/asm/percpu.h

Signed-off-by: Justin P. Mattock <justinmattock@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index 66a272d..9899afa 100644
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -105,7 +105,7 @@
 
 /*
  * Generate a percpu add to memory instruction and optimize code
- * if a one is added or subtracted.
+ * if one is added or subtracted.
  */
 #define percpu_add_op(var, val)						\
 do {									\