x86: clean up find_e820_area(), 64-bit

Change size to unsigned long, becase caller and user all used unsigned long.
Also make bad_addr take an alignment parameter.

Signed-off-by: Yinghai Lu <yinghai.lu@sun.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>