patmos: restructure context_switch for platin

arch/patmos/tcb.cc

@@ -53,10 +53,8 @@ void context_load(const TCB *to) {
 	"mts $s8 = $r15       \n"
         "nop\n"
 	"sens $r12	     \n"
-	"ret                  \n"
         "mts $s3 = $r11       \n"
 	"mts $s0 = $r9        \n"
- 	"nop"
         : : "r"(to->dynamic_context)
     );
 switch_context_load:
@@ -125,8 +123,6 @@ void context_save_and_load(const TCB * from, const TCB *to) {
 	"sens $r12	     \n"
         "mts $s3 = $r11       \n"
 	"mts $s0 = $r9        \n"
-	"retnd                \n"
-	"nop"
         : : "r" (from->dynamic_context), "r"(to->dynamic_context)
     );
 switch_context_save_and_load: