x86: cleanup: change _end to end_before_pgt

cleanup: change the _end in compressed vmlinux_64.lds.

also change _heap to _ebss that is not needed.

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>