openrisc: convert to setup_initial_init_mm()

Use setup_initial_init_mm() helper to simplify code.

Link: https://lkml.kernel.org/r/20210608083418.137226-11-wangkefeng.wang@huawei.comSigned-off-by: NKefeng Wang <wangkefeng.wang@huawei.com>
Acked-by: NStafford Horne <shorne@gmail.com>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
Cc: Stafford Horne <shorne@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

arch/openrisc/kernel/setup.c

@@ -293,10 +293,7 @@ void __init setup_arch(char **cmdline_p)
 #endif
 
 	/* process 1's initial memory region is the kernel code/data */
-	init_mm.start_code = (unsigned long)_stext;
-	init_mm.end_code = (unsigned long)_etext;
-	init_mm.end_data = (unsigned long)_edata;
-	init_mm.brk = (unsigned long)_end;
+	setup_initial_init_mm(_stext, _etext, _edata, _end);
 
 #ifdef CONFIG_BLK_DEV_INITRD
 	if (initrd_start == initrd_end) {