arm: convert to setup_initial_init_mm()

Use setup_initial_init_mm() helper to simplify code.

Link: https://lkml.kernel.org/r/20210608083418.137226-4-wangkefeng.wang@huawei.comSigned-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Acked-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/arm/kernel/setup.c

@@ -1130,10 +1130,7 @@ void __init setup_arch(char **cmdline_p)
 	if (mdesc->reboot_mode != REBOOT_HARD)
 		reboot_mode = mdesc->reboot_mode;
 
-	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);
 
 	/* populate cmd_line too for later use, preserving boot_command_line */
 	strlcpy(cmd_line, boot_command_line, COMMAND_LINE_SIZE);