fix spell wrong.

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@1920 bbd45198-f89e-11dd-88c7-29a3b14d5316

components/finsh/cmd.c

@@ -31,7 +31,7 @@
 #include "finsh.h"
 
 // Copy from kservice.h because we can not use it out of the kernel.
-// Ugly. Should let kservice.h avaliable for applications?
+// Ugly. Should let kservice.h available for applications?
 rt_inline int rt_list_isempty(const rt_list_t *l)
 {
 	return l->next == l;