arc: convert to setup_initial_init_mm()

Use setup_initial_init_mm() helper to simplify code.

Link: https://lkml.kernel.org/r/20210608083418.137226-3-wangkefeng.wang@huawei.comSigned-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Acked-by: Vineet Gupta <vgupta@synopsys.com>	arch/arc]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/arc/mm/init.c

@@ -89,10 +89,7 @@ void __init setup_arch_memory(void)
 {
 	unsigned long max_zone_pfn[MAX_NR_ZONES] = { 0 };
 
-	init_mm.start_code = (unsigned long)_text;
-	init_mm.end_code = (unsigned long)_etext;
-	init_mm.end_data = (unsigned long)_edata;
-	init_mm.brk = (unsigned long)_end;
+	setup_initial_init_mm(_text, _etext, _edata, _end);
 
 	/* first page of system - kernel .vector starts here */
 	min_low_pfn = virt_to_pfn(CONFIG_LINUX_RAM_BASE);