x86: lds - Use PAGE_SIZE instead of numeric constant

It's much better to use PAGE_SIZE then magic 4096
(though it's almost synonym in most cases on x86 but
not for *all* cases ;)

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>