ARM: 8471/1: need to save/restore arm register(r11) when it is corrupted

ARM: 8471/1: need to save/restore arm register(r11) when it is corrupted

commit fa0708b320f6da4c1104fe56e01b7abf66fd16ad upstream.

In cpu_v7_do_suspend routine, r11 is used while it is NOT
saved/restored, different compiler may have different usage
of ARM general registers, so it may cause issues during
calling cpu_v7_do_suspend.

We meet kernel fault occurs when using GCC 4.8.3, r11 contains
valid value before calling into cpu_v7_do_suspend, but when returned
from this routine, r11 is corrupted and lead to kernel fault.
Doing save/restore for those corrupted registers is a must in
assemble code.

Signed-off-by: Anson Huang <Anson.Huang@freescale.com>
Reviewed-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
[lizf: Backported to 3.4: adjust context]
Signed-off-by: Zefan Li <lizefan@huawei.com>