[Fix] pass x16 register as parameter for SBI call

The previous approach "li x16,0" may prevent the compiler from recognizing x16 as a function parameter, resulting in the caller saved register saving mechanism not being triggered in release mode.

Author: Azure-stars

os/src/main.rs

@@ -103,7 +103,6 @@ pub fn rust_main() -> ! {
     clear_bss();
     kernel_log_info();
     mm::init();
-    println!("after mm::init!");
     mm::remap_test();
     task::add_initproc();
     println!("after initproc!");

os/src/sbi.rs

@@ -15,11 +15,11 @@ fn sbi_call(which: usize, arg0: usize, arg1: usize, arg2: usize) -> usize {
     let mut ret;
     unsafe {
         asm!(
-            "li x16, 0",
             "ecall",
             inlateout("x10") arg0 => ret,
             in("x11") arg1,
             in("x12") arg2,
+            in("x16") 0,
             in("x17") which,
         );
     }