csky: remove syscall_exit_work

Remove syscall_exit_work and union all to ret_from_exception.

Signed-off-by: Guo Ren <ren_guo@c-sky.com>

arch/csky/kernel/entry.S

@@ -184,17 +184,9 @@ ENTRY(csky_systemcall)
 	stw	a0, (sp, LSAVE_A0)	/* Save return value */
 
 	movi    a0, 1                   /* leave system call */
-	mov	a1, sp			/* sp = pt_regs pointer */
+	mov     a1, sp                  /* right now, sp --> pt_regs */
 	jbsr    syscall_trace
-
+	br	ret_from_exception
-syscall_exit_work:
-	ld	syscallid, (sp, LSAVE_PSR)
-	btsti	syscallid, 31
-	bt	2f
-
-	jmpi	resume_userspace
-
-2:      RESTORE_ALL
 
 ENTRY(ret_from_kernel_thread)
 	jbsr	schedule_tail