Implement schedsleep() syscall to sleep a process for a given time

kernel/syscall/sched.c

@@ -9,3 +9,9 @@
 int32_t SYSCALL0(sys_schedrelease) {
   return E_DOSCHEDULING;
 }
+
+int32_t SYSCALL1(sys_schedsleep, ms1) {
+  uint32_t ms = (uint32_t)ms1;
+  hal_wait(ms);
+  return E_OK;
+}

kernel/syscall/sched.h

@@ -5,5 +5,6 @@
 #include "syscall.h"
 
 int32_t SYSCALL0(sys_schedrelease);
+int32_t SYSCALL1(sys_schedsleep, ms1);
 
 #endif // SYSCALL_SCHED_H_

kernel/syscall/syscall.c

@@ -27,6 +27,7 @@ SyscallFn SYSCALL_TABLE[SYSCALLS_MAX] = {
   [SYS_MMAN_UNMAP] = &sys_mman_unmap,
 
   [SYS_SCHEDRELEASE] = &sys_schedrelease,
+  [SYS_SCHEDSLEEP]   = &sys_schedsleep,
 
   [SYS_RAND]       = &sys_rand,