refactor(shell): mark shell_loop() as _Noreturn

Author: akbe2020

kernel/include/shell/shell.h

@@ -1,6 +1,6 @@
 #ifndef SHELL_H
 #define SHELL_H
 
-void shell_loop();
+_Noreturn void shell_loop();
 
 #endif

kernel/shell/shell.c

@@ -1,6 +1,6 @@
 #include <stdio.h>
 
-void shell_loop() {
+_Noreturn void shell_loop() {
     for (;;) {
         printf("\033[1;32m~$\033[0m ");
         char str[128];