[Update] chg rv to la

lasoft/xv6-la/kernel/entry.S

@@ -9,13 +9,13 @@ _entry:
         # stack0 is declared in start.c,
         # with a 4096-byte stack per CPU.
         # sp = stack0 + (hartid * 4096)
-        la sp, stack0
-        li a0, 1024*4
-        csrr a1, mhartid
-        addi a1, a1, 1
-        mul a0, a0, a1
-        add sp, sp, a0
+        la.global       $sp, stack0
+        li.w    $a0, 1024*4
+        csrrd   $a1, CPUID
+        addi.w  $a1, $a1, 1
+        mul.w   $a0, $a0, $a1
+        add.w   $sp, $sp, $a0
         # jump to start() in start.c
-        call start
+        bl      start
 spin:
-        j spin
+        b       spin