Set frame pointer right after stack allocation

riscv-rt/asm.S

@@ -68,12 +68,12 @@ _start:
     mul t0, a2, t0
     sub sp, sp, t0
 
-    // Park non-zero harts
-    bnez a2, abort
-
     // Set frame pointer
     add s0, sp, zero
 
+    // Park non-zero harts
+    bnez a2, abort
+
     jal zero, _start_rust
 
     .cfi_endproc