arch/risc-v: remove duplicated nxsched_switch_context() call

The nxsched_switch_context() function should only be called
    when a task switch actually occurs. The RISC-V architecture
    already performs this call in riscv_perform_syscall(),
    so this PR removed the redundant nxsched_switch_context() call in
    up_switch_context().

Signed-off-by: Chengdong Wang <wangchengdong@lixiang.com>

arch/risc-v/src/common/riscv_switchcontext.c

@@ -80,12 +80,6 @@ void up_switch_context(struct tcb_s *tcb, struct tcb_s *rtcb)
 
   else
     {
-      /* Update scheduler parameters */
-
-      nxsched_switch_context(rtcb, tcb);
-
-      /* Then switch contexts */
-
       riscv_switchcontext();
 
       /* riscv_switchcontext forces a context switch to the task at the