ARM: kernel: refer to swapper_pg_dir via its symbol

maillist inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I8KNA9
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/ardb/linux.git/commit/?h=arm-kaslr-latest&id=fe64d7efe89877bc52454f9f2bc9ab0ce01ae8fc



-------------------------------------------------

The location of swapper_pg_dir is relative to the kernel, not to
PAGE_OFFSET or PHYS_OFFSET. So define the symbol relative to the
start of the kernel image, and refer to it via its name.

Cc: Russell King <linux@armlinux.org.uk>
Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Felix Fu <fuzhen5@huawei.com>