scripts/link-vmlinux.sh: only filter kernel symbols for arm

scripts/link-vmlinux.sh: only filter kernel symbols for arm

Actually CONFIG_PAGE_OFFSET isn't same with PAGE_OFFSET, so
it isn't easy to figue out PAGE_OFFSET defined in header
file from scripts.

Because CONFIG_PAGE_OFFSET may not be defined in some ARCHs(
64bit ARCH), or defined as bogus value in !MMU case, so
this patch only applys the filter on ARM when CONFIG_PAGE_OFFSET
is defined as the original problem is only on ARM.

Cc: <[email protected]>
Cc: Rusty Russell <[email protected]>
Fixes: f6537f2f0eba4eba3354e48dbe3047db6d8b6254
Singed-off-by: Ming Lei <[email protected]>
Signed-off-by: Rusty Russell <[email protected]>