Fixed function spelling mistakes in context_iar.S

swtich_to_thread -> switch_to_thread

libcpu/rx/context_iar.S

@@ -73,12 +73,12 @@ ___interrupt_27:
     MOV.L    #_rt_interrupt_from_thread, R15
     MOV.L    [ R15 ], R15
     MOV.L    R0, [ R15 ]
-    BRA      swtich_to_thread
+    BRA      switch_to_thread
 need_modify_isp:
     MVFC     ISP, R15                
     ADD      #12, R15
     MVTC     R15, ISP
-swtich_to_thread:
+switch_to_thread:
     SETPSW   U
     MOV.L    #_rt_interrupt_to_thread, R15
     MOV.L    [ R15 ], R15