Fix _FPC_xtensa_exit first parameter passing

rtl/linux/xtensa/si_c.inc

@@ -53,7 +53,7 @@ procedure _FPC_proc_start; assembler; public name '_start';
 
 procedure _FPC_xtensa_exit(e:longint); assembler;
   asm
-    mov a6,a3
+    mov a6,a2
     movi a2,119
     syscall
   end;

rtl/linux/xtensa/si_dll.inc

@@ -32,7 +32,7 @@ procedure _FPC_shared_lib_start(argc : dword;argv,envp : pointer); cdecl; public
 procedure _FPC_shared_lib_haltproc(e:longint); cdecl; assembler; public name '_haltproc';
   asm
   .L1:
-    mov a6,a3
+    mov a6,a2
     movi a2,119
     syscall
     j .L1

rtl/linux/xtensa/si_prc.inc

@@ -55,7 +55,7 @@ procedure _FPC_dynamic_proc_start; assembler; public name '_dynamic_start';
 procedure _FPC_xtensa_exit(e:longint); assembler;
   asm
   .L1:
-    mov a6,a3
+    mov a6,a2
     movi a2,119
     syscall
     j .L1

rtl/linux/xtensa/si_uc.inc

@@ -92,7 +92,7 @@ procedure _FPC_proc_start; assembler; public name '_start';
 
 procedure _FPC_xtensa_exit(e:longint); assembler;
   asm
-    mov a6,a3
+    mov a6,a2
     movi a2,119
     syscall
   end;