common-user/host/sparc64: Fix safe_syscall_base

Use the "retl" instead of "ret" instruction alias, since we
do not allocate a register window in this function.

Fix the offset to the first stacked parameter, which lies
beyond the register window save area.

Fixes: 95c021dac835 ("linux-user/host/sparc64: Add safe-syscall.inc.S")
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

common-user/host/sparc64/safe-syscall.inc.S

@@ -24,7 +24,8 @@
         .type   safe_syscall_end, @function
 
 #define STACK_BIAS  2047
-#define PARAM(N)    STACK_BIAS + N*8
+#define WINDOW_SIZE 16 * 8
+#define PARAM(N)    STACK_BIAS + WINDOW_SIZE + N * 8
 
         /*
          * This is the entry point for making a system call. The calling
@@ -74,7 +75,7 @@ safe_syscall_end:
         /* code path for having successfully executed the syscall */
         bcs,pn  %xcc, 1f
          nop
-        ret
+        retl
          nop
 
         /* code path when we didn't execute the syscall */